USCIS will tell us when they announce that the cap has been reached what they are doing with pending cases (It looks as if they are counting cases toward the cap as they come in so anything that is filed should be ok, but don't quote me).
On the good side, USCIS has apparently backpedaled, slightly, from their previous ominous statement. Now they say that the cap is near but it is too early to tell exactly when it will be reached.