I dunno, I'm a homebrewer, but even
I'm a bit tempted by Eberron...I don't think I'll be buying many of the supplements (well, mabe the D&D online game) beause I am such an avid homebrewer I'd like to take the world and screw it in my own particular fashion (like how I introduced the Cthulu Mythos to FR....with as many magical mysteries as those guys plumbed, it was GREAT!). But still, the fact that I may run the setting, with only the most minor of changes (I think the Warforged are too powerful and you shouldn't need a feat to multiclass, etc.)....I'm scared....homebrewers, please, hold me, tell me it'll be okay...
The Realms ain't goin' anyplace....they may get less (fewer regional supplements, probably), but they'll linger, there will be new core books, new supplements, new things updating FR for the novel line (WotC will keep the liscence if only for that!), etc.
But I think the perception at WotC is that the Realms has basically reached all the customers it's going to for the moment...time to get some new dollas with something that'll reach some of the same, some of the new.