No, you aren't seeing things, people: Lost Planet 2 will apparently feature appearances by Gears of War main duo Marcus and Dom.
Today must be "Strange Capcom News Day," by the looks of things: One of the more unexpected pieces of news to come out of the Microsoft Vs. Capcom announcement bonanza was the trailer you see above here for the upcoming Lost Planet 2. In the video, two Lost Planet soldiers are ambushed by a vicious alien foe, but they soon receive backup from a very unlikely source: COG Delta squad frontmen Marcus Fenix and Dom "Bawwwwwwww My Wife" Santiago. Marcus and Dom are, of course, very familiar with fighting alien bugs - but different alien bugs. They fight the Locust, not the Akrid. Totally different things, guys.
Given that Gears of War is made by Epic Games and not Capcom, it's safe to say that probably nobody saw this coming (though if you follow Cliffy B on Twitter, this would appear to be the "kick-ass news" the guy has been Tweeting about). On the other hand, it does make sense in a way - Lost Planet 2 designer Jun Takeuchi has been a very fervent admirer of Epic's Gears of War games, even going so far to say that the controls in his Resident Evil 5 were influenced by the games (though sadly, RE5 did not feature chainsaw rifles).
It's currently unknown just what form the Dom & Marcus cameo will take - will they be in the story mode? Will they be downloadable or unlockable characters for the multiplayer? Will they be appearing on the PS3 version too or just the Xbox 360 version? We don't know. All we know is that crossovers between different development studios are still awesome, and the world needs more of them.
I'm calling Jill Valentine and Chris Redfield as bonus characters in Gears of War 3 right now. Just for the record.