I think that other than reasons, nothing will close until Labor Day. Shrek and Guys and Dolls will at least last until then, what with name recognition alone during the touristy summer months. But I expect both, especially Shrek to die hard when school gets back in session.
Rock of Ages, Billy, West Side Story, and Hair will both be just fine for a while, for different reasons of course.
And I have a good feeling about the future of next to normal. I wouldn't have thought this when it opened months ago, but I think it has built up a strong fanbase and word of mouth. I believe it will last at least through the summer, and longer. The performance only helped it, as many of my friends who already were not interested in the show now are. Ticket sales are keeping steady enough that it really will catch on, if it hasn't already.
"Art, in itself, is an attempt to bring order out of chaos."-Stephen Sondheim