David Uzumeri (who you may know from Funybook Babylon and the Savage Critics) posted a link to the Diamond order form for April 2010's books on Twitter and it includes a few very interesting books from Marvel. I'll discuss that in more detail below the cut to avoid possible spoilers...
Some of the books shipping in April apparently:
New Avengers Finale #1; something called Fallen, five Siege-related one-shots devoted to Loki, Spider-Man, Captain America, Young Avengers, and Secret Warriors; Captain America: Who Won't Wield the Shield #1; Thor and the Warriors Four #1 (listed apart from the Siege books, though). Plus a few others like the second Ultimate Comics Avengers arc restarting the series instead of being solicited as issue seven, a Deadpool Corps series, and the appearance of Philip K. Dick's Electric Ant #1 by David Mack finally.
Edit: As was pointed out in the comments, IGN's solicits preview reports that all four Avengers ongoings are ending in April.