I would, but it creates a significant cascade of glass upgrades on top of the body purchase. First and foremost would be the 17-55mm f/2.8 EF-S. I would probably also want to trade out the 85mm f/1.8 for a 135mm. Hence my choice to be satisfied with what I have.
I guess this is where Nikon has an advantage where you can still use DX lenses on their FF bodies... at least until you're ready to upgrade whichever lenses you find need.
The D800, in particular, seems like Nikon might really have had that in mind. I've been using my 17-55mm DX f/2.8 on it in 1.2x crop mode for the last couple weeks, and it's working out quite well even if not exactly ideal -- 1.2x crop still yields ~25MP images, and DX crop yields ~15MP. In 1.2x crop, there's a little bit of vignetting until circa 24mm-on-up, and I find the little bit of vignetting from circa 21mm to 24mm acceptable most times in my case -- well, I do also have to remove the lens hood at these wide angles most times as the hood can add to the vignetting. At 21-to-22mm, 1.2x crop yields roughly the same FOV as 17mm in DX crop, and 24mm in 1.2x crop is equiv to ~29mm FF. I do also have a Sigma 20mm f/1.8 FF prime, but haven't felt a real need for it so far. Then again, I don't usually shoot landscapes, and I'd think the vignetting would be more problematic for that...
For the school musical that my son's in right now, I've also found it helpful to be able to switch quickly between FF, 1.2x and DX crops in the camera, particularly while shooting video and using my Sigma 70-200 f/2.8 (and can't really move around much). Video doesn't need the extra MPs although I'm not sure if IQ is impacted anyway due to use of cropped portion of sensor...
Anyway, at this point, I don't really feel compelled to buy new glass yet. Yeah, would be nice to replace the 85 f/1.8 w/ a 105mm or 135mm prime, but I'm finding that not so necessary anymore -- well, I do have an old 105 f/2.8 manual micro prime, but that's quite diff. For one thing, f/2.8 (or even f/4) is usually fast/open enough on the larger sensor before overly shallow DoF becomes an issue, and I do have most of my shooting range covered w/ f/2.8 glass, if not better.
Just another amateur learning to paint w/ "the light of the world".
"Whatever is true, whatever is honorable, whatever is right, whatever is pure, whatever is lovely, whatever is of good repute, if there is any excellence and if anything worthy of praise, dwell on these things..." (Apostle Paul)