Siliconera reports that a recent post by Capcom Senior Vice President Christian Svensson states that "Our rights with Tatsunoko have lapsed fairly recently (so we're no longer allowed to sell the title physically or digitally)." So what you see out there now is pretty much it; if you want a copy, then be sure to grab it.
And why wouldn't you? In addition to the Capcom fighting game quality we've come to expect (barring the whole downloadable content aspect of late), it features a nice variety of Mega Man characters as well: Roll from the Classic series with a new move set, Zero from Mega Man X, and the one-and-only fighting game appearance of MegaMan Volnutt from Mega Man Legends, complete with a Gesellschaft stage occupied by Servbots. Plus, Frank West dons his X-flavored duds for the occasion as well.
Matthew Green on Press The Buttons also adds this insight:
Capcom's discontinued fighting games hold their value long past their expected expiration date. Prior to Marvel vs Capcom 2 returning for the Microsoft Xbox 360 and Sony PlayStation 3 a few years ago, used copies of the game for older consoles still commanded absurdly high prices, for instance.
Svensson added that he didn't foresee anything new to come from their involvement unless Japan forges a new deal, and who knows when that could happen? So if you want to enjoy the game, now is the time to buy... even if you just want to hold on to it until you get a Wii U, or just a good deal on a Wii. After all, it took a decade before Marvel vs. Capcom 2 became easily-affordable and accessible again.