Bioware has always maintained that it intends to be a developer that splits its time between consoles and PC games. We did do MDK2, after all (which came out first on console), and any console games that are upcoming are just more efforts along that line.
I'm not sure I understand the sentiment behind some of the posts here, myself. It seems, to some people, that if Bioware does a game for a console it's as if we switched to another medium altogether (like a rock singer who decides to go and write poetry).
It's not as if the X-Box (or any console) doesn't have its own RPG fans who we would like to reach, as well. Why are they so undeserving of our attention?
Developing for a console has its own plusses (such as the lack of a need to worry about different hardware configurations and compatibilities) and negatives (like the lack of a keyboard and therefore a need to specially-design the GUI to handle the limitation). It's no different then designing for the PC... in fact, most console games can be ported to the PC (as was mentioned) if demand warrants it, whereas the same is not true in reverse unless the interface is specifically such that it can work on a console.
At any rate, as has been mentioned a PC-only game is in the wings, as well. Nothing is being abandoned and we are well-able to work on several projects at once (and have for quite some time). No Microsoft Conspiracy here... just Bioware having the opportunity to work with the right companies that fit the projects we want to work on. Hopefully, in the end, all gamers benefit.