I don't think I'd ever want to go FF only. You have so many more options with two formats. As long as Canon makes 1.6 crop bodies and EF-S lenses, I'll keep using them. The sheer amount of detail I see in my 1Ds3 shots is amazing, but in reality a bride isn't gonna care or notice if their album spread or their huge canvas has a little less detail, especially if they don't have a basis of comparison.
I want a 7D; it's such a cool camera. But I've tried them and in wedding shooting it doesn't get me shots any better than my 40D, so I haven't bought one. One shot AF didn't seem any better than my 40D. Actually, I liked the 40D raw files better... the 7D has many more pixels, but comparing the two I didn't see any more detail. I'm looking for an excuse to buy one but I just haven't yet. I can't complain, I really do love my 40D and it's all the camera I need in weddings 95% of the time. The other 5% is where the 1Ds3 comes in.