Samuel L. Jackson portrays Dr. Martin Luther King, Jr., left, and Angela Bassett portrays Camae in Katori Hall's play "The Mountaintop," at the Bernard B. Jacobs Theater in New York. (Joan Marcus/AP PHOTO/THE O+M COMPANY, JOAN MARCUS)

In an art form powered by illusion, dreaming turns out to be the easy part.

Marvelous designs are laid out; visionary projects are greenlighted; exciting partnerships announced, to fanfare and applause.

And then reality sets in. Yes, even in the theater.

Some unsettling signs of an unfortunate truism — that the big plans of theater-makers sometimes exceed their ability to implement them — have come to light in recent weeks, for two theater companies with deep roots in the region. The disappointing results, one hopes, will not be an impediment to further dreaming. But they should be viewed as cautionary moments in increasingly stressful times for the performing arts.

At Arena Stage, comes the dispiriting news that at the end of a two-year paid residency, the up-and-coming playwright Katori Hall has left the New Play Institute program, according to Arena officials. Her departure comes short of one of the project’s stated goals: having one of her new plays — or an older play, reworked — staged during her time here. Instead, Arena is simply presenting Hall’s “The Mountaintop” — a play that has already been done on Broadway and in London — in a co-production with Houston’s Alley Theatre. And at one of the region’s resilient smaller mainstay companies now known as WSC Avant Bard, there’s a more dire turn of events. Two years into WSC’s own residency, in Arlington’s Artisphere, the county has informed the troupe that because it wants to make more money with shorter-run rentals, WSC has to go.

What these disparate happenstances share is a sense of expectations rapidly raised and then almost as quickly dampened; in Arena’s case, one feels some deflation of the hope that an uptick in writerly energy, fostered by the two-year-old residency initiative, would have ignited the institution’s programming — or at least yielded something immediate by one of the higher-profile dramatists among the five initially selected for coveted salaried spots.

And for WSC, formerly called Washington Shakespeare Company, its mid-season eviction from the Artisphere — after losing its former longtime home in the Clark Street Playhouse — feels like an untimely and undeserved slap in the face. It signals a crisis that will deprive it of a most becoming black-box space in Rosslyn, and quite possibly, the full menu of offerings it has promised to playgoers this spring.

With the job of managing the programs and finances of nonprofit arts organizations becoming ever more difficult, these unsettling outcomes do not engender confidence in the future. Credibility and continuity are among a theater company’s most important assets. With Hall’s unsatisfying exit, the former is at risk in the program at Arena, and with Arlington’s cultural affairs division kicking a theater troupe to the curb, the latter is now in tatters at WSC. The county is vowing to help WSC — whose focus often is reinterpretation of classic drama — locate alternative digs. But the treatment of the company is shabby, particularly for a local government that prides itself on civic support for the arts.

Christopher Henley, WSC’s founding artistic director, says the black box space in the Artisphere, which opened in October 2010 in the former Newseum space in Rosslyn, was taken away from WSC in a meeting on Dec. 11, a casualty of the arts center’s dismal track record. (The county is suggesting Henley move at least part of the time to the uninviting Theatre on the Run, in a dreary office building in Shirlington.) From the start, the county projections for how many people would visit Artisphere were almost laughably overstated : on the occasions I visit, the attractively refurbished complex feels like a public hall in a ghost town.

WSC was never destined to pack ’em in. The troupe goes in for reinterpreted classics, sometimes in smart ways, as with its fine revival of Schiller’s “Mary Stuart,” and sometimes wackily, as demonstrated by its naked “Macbeth.” But shouldn’t that have been part of the calculation when the company was granted tenancy there for 32 weeks a year? Henley says that historically, both at Clark Street and Artisphere, he essentially has had a handshake relationship with the county.

“In terms of having things contractual and on paper, it’s never happened with us,” Henley says, adding that in WSC’s first two years at Artisphere, “we had nothing except the understanding and we’d agree on a calendar.”

A more strategic approach by both the company and its government landlord might have prevented this sad outcome. In any event, the net result is an established Washington company displaced and a theater space lost to troupes with long-term visions.

What’s being squandered in Arena’s playwright residencies — unveiled as front-page news back in June 2010 — is momentum. As part of a $1.1 million grant from the Andrew W. Mellon Foundation, Arena brought into the institution five writers, each provided a substantial yearly stipend, health benefits and a separate pool of development money, to be used for workshop productions and the like. The residencies were supposed to be for three years, though Hall stayed for only two.

In the 2011-12 season, Arena produced comedies by two of the five writers: reworkings of Karen Zacarias’s “The Book Club Play,” originally done at Round House Theatre, and Amy Freed’s “You, Nero.” No work by any of the writers is on the Arena boards this season. (The other playwrights are Charles Randolph-Wright and Lisa Kron; Sam Hunter, author of “A Bright New Boise,” produced at Woolly Mammoth Theatre, was recently added to the roster for a one-year residency.) Arena says that the residencies were never intended as a commissioning vehicle for new work, that the choice of what of theirs Arena might produce was up to the playwrights themselves. So one is compelled to wonder: was this program, part of the American Voices New Play Institute, mislabeled? Should Arena theatergoers have been better apprised about the meager early rewards?

Make no mistake: Play-creation is a painstaking process, difficult to place on a timetable. It requires patience all around. Certainly, Hall gained from the experience at Arena. On a Web site blog, the theater noted that the playwright “experienced a deep artistic connection with the Arena staff members,” did “extensive research” on a new play, and had readings of two others. (It should also be noted that Hall enjoyed a concurrent residency at New York’s Signature Theatre, where her play “Hurt Village” premiered last March.)

Arena’s residency program remains full of promise for American playwriting. But it needs to generate more tangible results for audiences here. If it doesn’t, it probably will, like WSC at the Artisphere, overstay its welcome.