MLS has been so good with expansion decisions the past 10 years, we have become spoiled by newcomers seamlessly assimilating with the old guard and raising the quality and profile of the ambitious league. Imagine the modern-day circuit without the Pacific Northwest, without the Canadian clubs, without Philadelphia and Salt Lake City and the return to the Bay Area.

In growing first-tier pro soccer and expanding the North American footprint from 10 clubs a dozen years ago to 21 next spring, MLS has gotten it mostly right. (Miami Fusion and Chivas USA were the exceptions since the 1996 launch.)

But as the next growth spurt approaches, one can’t help but wonder whether blind ambition, not to mention lucrative expansion fees, have clouded MLS’s judgement.

Of the four arrivals, only Orlando makes perfect sense: an organically grown fan base and a certain stadium project in a city with only one other pro sports team.

The others — New York City FC, Miami and Atlanta (to be announced Wednesday) — are suspect. New teams do not need to match the success of their predecessors — Seattle, Portland and others have set the bar a mile high — but they do need to meet rising expectations.

On Monday, the New York Times reported NYCFC will play three seasons at a baseball yard, Yankee Stadium. (Ask D.C. United and the Washington Nationals how well that arrangement went at RFK Stadium in 2005-07.) In a rush to introduce a second Big Apple club and collect Abu Dhabi and pinstripe cash, MLS fast-tracked a team without a stadium plan. Just when MLS had almost completely weaned itself from awkward and long-term stadium-sharing deals, along comes another — forced into a metropolitan area that already has a stable MLS team within a short train ride of Manhattan.

Eventually, NYCFC will build a stadium of its own. Maybe in Queens, perhaps the Bronx. But without any firm plans in place, three years at Yankee Stadium could easily turn into five. Yankee Stadium can accommodate soccer — it has done so several times in recent years for high-profile friendlies — but it’s not a soccer stadium. It’s not even an NFL venue. Gillette Stadium is an imperfect home for the New England Revolution, but at least it offers proper shape and sightlines. (With NYCFC at Yankee Stadium, the Revs surely must now move to Fenway Park and change their name to the Rev Sox, taking the Boston-New York sporting hatred up another notch!)

Next, we turn a skeptical eye to Miami, David Beckham‘s playpen. MLS awarded a team but without a specified timetable or stadium plan. Formal entry into the league is contingent on Beckham using his ample bank account and dreamy smile to arrange a venue project, preferably on the waterfront. So far, no luck — and growing resistance.

Even with an arena, South Florida is a questionable destination. The region already lost an MLS team — although in fairness, that club lacked deep investment and played in north Fort Lauderdale, a long drive from Miami’s international vibe. The deeper concern is Miami’s appetite for pro sports. Setting aside the NBA champion Heat, the Marlins were 28th of 30 in MLB attendance last year (in a new stadium!); the Florida Panthers were 29th of 30 in the NHL this season; the NFL’s Miami Dolphins were 30th of 32 in percentage of their stadium filled for eight home games last year.

Unlike Orlando, an MLS club in Miami would have to fight for customers in a saturated, and lackluster, pro sports market.

Miami overflows with international diversity, particularly Latin American. But the Cuban community follows baseball, and the Argentine, Brazilian and Colombian expats following European and South American soccer may not have an appetite for local MLS. Would fans with Central American roots help support it?

MLS’s third foray into southern states is Atlanta. Using a wall map with pins to indicate current MLS markets, it’s easy to understand why the league is looking to that part of the country to grow. At the moment, there are no teams playing south of Washington on the Eastern seaboard — an enormous, untouched footprint. Atlanta is also the largest U.S. or Canadian market without an MLS presence.

But does Atlanta make practical sense? Like with Miami, it’s no tap-in from six yards. Both are major cities with several established sports franchises (not to mention a passion for college sports and auto racing). Atlanta, too, suffers from attendance issues: While the NFL’s Falcons are a hit, the hockey team left in 2011, the Braves are middle of the pack (and abandoning downtown for the suburbs) and the NBA’s Hawks are 28th of 30.

Atlanta’s recent pro soccer history is modest: The NASL’s Silverbacks have been around, in one form or another, for almost 20 years, setting an organization attendance high last year with an average of 4,677. Mexico’s national team has drawn monster crowds at Georgia Dome, but El Tri would attract an audience in Montana.

The drive behind the Atlanta effort comes from the Falcons, and more specifically, Falcons owner Arthur Blank, the Home Depot co-founder who will permanently house the MLS team in a stadium designed primarily for the Falcons with a retractable roof and artificial turf. Except in Seattle, where CenturyLink Field works well for MLS for so many reasons, the league should be veering from NFL stadiums, not toward them.

With Orlando, NYCFC, Miami and Atlanta, MLS will have filled 23 of presumably the maximum 24 clubs. (It’s still unclear what will happen with Chivas USA after this year, though Commissioner Don Garber said the team will remain in the Los Angeles area. Real questions will arise about D.C. United’s future, should the Buzzard Point stadium proposal fall victim to politics.)

Which city will receive the last expansion prize? Minneapolis is proposing a soccer-specific downtown stadium. San Antonio wants in. Sacramento is eager.

Expansion is, for the most, a good thing for MLS. It’s a sign of the league’s — and the sport’s — growth. Some may argue MLS should follow the lead of top leagues around the world and cap the number of first-tier teams at 20. But the U.S. population is larger than the combined total of Germany, Italy, England, Spain and France; if American cities are genuinely interested in MLS, the league should hear them out.

MLS, however, also needs to look beyond the tempting expansion fees ($70 million-$100 million) and get past the idea of expanding just for the sake of expansion. Who knows: Maybe Atlanta is the next Seattle, Miami mimics Toronto and NYCFC forges an authentic derby with the Red Bulls. Still, though, it’s imperative to take a hard look at long-term viability in future markets.