Buy now. Enjoy using your gear in the meantime.
I held back on buying a 5D for a long time waiting for the 5D mkII, then ended up getting a mkI anyway when it was released (the specs of the mkII were not what I'd hoped given the price)!
There will allwyas be new models as you say. Also when new cameras are released the price is very high, there are are often problems with supply, firmware bugs and other issues that are noticed by early adopters which take time to fix. It's much better to wait a while until all the faults are ironed out and a user base develops, helping evaluate the camera.
The only exceptions are truly game changing features such as Nikon's first FX camera (and perhaps video). Other than this updates are incremental and not worth the wait.