Interesting speculation, but I think it's just wrong. Apple hasn't been interested in being in the gaming console market for more than a decade. For the vast majority of game manufacturers, making their games run on Macs is an afterthought if ever at all. Already they must consider four versions of their games: Xbox, PS2, GameCube, and PC, and as most gamers know, some games never make even to the four major platforms. And now....if this speculation is correct, they'd have to consider a very small 5th platform? It's just not going to happen, even if the new Mac mini can run PC games natively (Wine-like execution layer, Windows-native OS, etc.). Furthermore, Microsoft has been buying their way into the gaming market for years, taking a loss on every Xbox ever sold (to the tune of $300 on each Xbox 360) and they're still not "killing" their competitors Sony and Nintendo.
Apple doesn't need to be in the gaming console market to succeed in creating a successful media center product. Simply creating a product that's attractive and easy-to-use--perhaps incorporating a nice programmable remote control--product to play media content from our PCs and from the iTunes Store will be enough to make it successful.