"City Dance '77," the recent festival of Washington dance troupes at the Warner Theater, was by common agreement a grand success. What remains in its wake, however, is the question, now what? Was this merely a heartwarming flash, or does it have significant implications for the future of dance in this city? What, if any, are likely to be the enduring effects of the event - once the momentary euphoria it generated is gone - on the participating companies and their audience?

Some time may have to pass before all the answers become apparent. But some things are already clear. The immediate purposes of the festival were gratifyingly accomplished.The participant troupes - the Maryland Dance Theater, the Washington Ballet, the Capitol Ballet, the Washington Dance Theater, the D.C. Repertory Dance Company, the Dance Construction Company and the African Heritage Dancers and Drummers - got to show their wares in a genuine, comfortable proscenium theater at the crossroads of a reawakening downtown.

All three evenings drew sizable crowds (upward of 1,200 on the two best nights). The audiences were delighted, ecstatic even, with what they saw. And the companies, revved up by the nature of the occasion, in many instances outdid their own best efforts of the past.

Beyond the sense of night-to-night triump, however, were the larger lessons. Putting all these outfits together, in one central and spotlighted place, had a remarkable mangifying effect. The individual troupes looked more formidable, more effective, more professional, in this clearly professional ambiance, than they tend to seem in their more customary, parochial surroundings. To be sure, shortcomings were made conspicuous along with strengths, and some companies benefited more from the transposition than others.

The Washington Dance Theater, for example, whose usual habitat is schools and churches, had its repertory enhanced by the possibilities of sophisticated stagecraft in the Warner, but the technical lapses of the dancers were perhaps more obvious in this setting than they would have been in less formal places. The African Heritage Dancers and Drummers, on the other hand - which also performs mostly in educational settings - looked more brilliantly virtuosic than ever; one could even see them managing a hit on Broadway, with this kind of vim and projection.

In any case, the juxtaposition of participants on the festival programs was a boon to all of them. Far from emphasizing weaknesses, the effect was to underscore the splendid diversity of style and substance among them, as well as the cumulative impressiveness of Washington's home-grown dance as a whole.

There were other kinds of fallout with important implications for the future. The cross-fertilization of audiences, for example. Each of these companies has played in the past to crowds of comparable size. But almost invariably, they have drawn upon a limited, "natural" constituency, based on stylistic preferences, racial factors and geographical convenience. The Warner programs broke down these barriers. The Capitol Ballet played for the Maryland Dance Theater audience, as well as its own.The fans of the Dance Construction Company stayed to see and applaud the African Heritage troupe, as well as the experimental ensemble that lured them.

What's more, from the brisk last-minute ticket sale, the long lines at the box-office and the crowd reactions during the performances, one infers that there was also a large segment of the audience new to dance performance altogether, attracted by the festival and attending perhaps on impulse. And the crowds were noticeably more integrated than any other of the city's usual dance audiences.

The festival also resoundingly proved not just the viability but the great appeal of the rehabilitated Warner for dance, despite some real technical problems including a severely limited wingspace. The drawbacks, though, are more than compensated for by the advantages of the theater's graciousness, its practically and its ideal location, a stone's throw from the Mall, shopping, restaurants, parking and the Metro. And the turnout showed that the new downtown image is actually taking hold - people will come downtown, even at night, if you give them something worth coming to.

The success of this first "City Dance" leads naturally to thoughts of an annual sequel, as well as Warner bookings for other dance events throughout the season. There are a goodly number of Washington-based troupes which deserve this kind of showcasing but could not be represented the first time out.

Bringing people to the dance, though, was only half of the original "City Dance" concept. The complementary - and equally consequential - notion was bringing dance to the people. It's worth noting that the Washington Performing Arts Society, which sponsored the festival, has already indicated that "City Dance '77" was a "first step before pursuing long-range plans of sending resident companies of professional dancers into the neighborhoods."

It's clear that to make large numbers of converts to the art and pleasure of dance throughout the community, it's not enough to wait for the prospects to beat upon your doors - you must seek out people where they live, and give them a dance experience that makes sense in their accustomed environments. "City Dance" is not just a step in this direction, it is an open portal, through which the future beckons.