Firstly, why would you want to buy a full frame? Its not really important for most uses.
I'm strongly contemplating upgrading to either of these two cameras from my current camera - a Nikon D40 (with 18-55 lens + 55-200 VR + sb-400).
The camera I have is perfectly good but sometimes I feel a bit limited to have to go through the menu, low light limitations and a general feeling that I have probably pushed it enough.
I rarely shoot wildlife or birds. I mostly shoot architecture, art details on temples, forts, palaces, old buildings, some culture and cityscape. I don't want a P&S or a bridge camera as I already have a DSLR and dont see myself going back.
Depends on what you want to shoot. You may not want to shoot everything. If you do, then perhaps getting one of those canon and nikon compacts with some huge zoom ratios may help. I have a friend who shoots around with one of these and gets stunning bird shots.
I can't afford all of them, and I certainly don't want to carry very many. :)
Every lens is the best lens :)