Yesterday, we learned of the upcoming Batman/Detective Comics crossover Night Of The Owls from the official DC Source blog.

But also at the Superman Homepage, Matt Idleson talked about a Superman, Superboy and Supergirl crossover this summer. He wrote;

Many things that will be factors in ACTION this year are being established in issues #5-6, Frank. Grant (with the help of guest-artist Andy Kubert) has sprinkled an incredible amount of fun hints inside a really challenging story. Meanwhile, Keith and Dan are plotting some really star-spanning stuff for Supes, though before that we'll be doing an event between SUPERMAN, SUPERGIRL and SUPERBOY in the summer. Superman hasn't met Superboy yet, and his relationship with Supergirl isn't exactly lovey dovey. Seeing how they function as a unit under those circumstances should be interesting, to say the least.

Also, it looks like Action Comics being set in the New DCU's past may continue for some time.

As hinted in another answer, Action Comics #9 is likely to be focusing on an element of the Multiverse, whilst the current origin storyline in Action Comics #5 and #6 will be laying groundwork for the coming year's worth of stories.

Finally, Matt also mentioned that we will be seeing Silver Banshee as a villain in one of the super-books, but not which one…