I haven't used my Nikon gear in weeks. The reason? m4/3! Three bodies (GH1 x 2 and a GH2) plus 3 zooms (7-14, 14-45 and 100-300) weighs less than the D2Xs with 80-200 AF-S. The plan was to buy a D600 to replace the other Nikon bodies, but after buying the Zuiko 75mm f/1.8 for m4/3 yesterday, I've started to wonder if I'll use it much. Instead, I consider the Panasonic 12-35 and 35-100mm f/2.8 and obviously the 42.5mm f/1.2 when it is launched some time next year. All stellar lenses, all smaller, lighter and cheaper than their full frame equivalents.
Just like we see MF users move towards 35mm gear like the D800, I think we'll see a lot of DSLR users move to mirrorless systems. They are smaller, cheaper and the quality, sensor as well as optical, keeps getting better every day. I tried the GH3 the other day. The ergonomics are at least on par with any Nikon camera that I've used, with the possible exception of the F6, but that's yet another world.
Nikon (and Canon) have to watch out, but I think they do. I wouldn't be surprised if the Nikon 1 system outsell traditional Nikon DSLRs in 5 years.