bodies are never a good investment
But i think you answered your own question about jumping the gun.
The only places I saw real improvement was the auto focus, and obvious the the frames/second. Also some nice features, video.
Overall, if you are not shoot a great deal of action or do not require video, you will be hard pressed to tell the different between the cameras!
I like your comment about the lenses you 'need' vs the ones you 'want'. Once you get the ones you 'need' the ones you want will becomes the ones you 'need' happens to the best of us. Not long ago I was saying the 10-22mm was the last lens i needed.