Rein cited resource concerns, saying that the company is more focused on pushing the limits of PlayStation 3 and Xbox 360. Interestingly, Rein also commented how making Wii graphics engines is not that profitable. "I think unless you're going to sell your engine to Nintendo, you're going for scraps on that platform," he said.
That point has been brought up before, how developers are not interested, and possibly lazy, in developing for the Wii platform and that their budgets for that platform are pretty low. However, from the perspective of a game developer, perhaps Epic could find a way to convert Unreal Tournament 2004 onto Nintendo's platform. The software alone would be profitable, we imagine, and then they'd have Unreal Engine 2 to license out.
Update: As it has been pointed out in the comments below, some Wii titles such as Red Steel do utilize Unreal Engine 2 -- optimized for the GameCube (keep the jokes to yourself, for now). However, we'd be interested to see Epic take the engine an optimize for the Wii's hardware upgrade.
Also, some people seem to be confused by Rein's profit comment. The profits for Epic wouldn't come from game sales but from licensing out the engine. Since most developers don't focus on the graphical prowess of their Wii titles, Epic would not be able to charge much for their engine -- hence why Rein doesn't feel the Wii would be a profitable venture for them.