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 allways be new models as you say. Also when new cameras are released the price starts 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). That's the only thing I would take into account, asking myself "does this new camera do something that was impossible before?", if not why wait.
Renting is an option, if you only expect to shoot infrequently, though this is a better approach for lenses. With camera bodies it pays to really learn all the features and get used to using it, which takes time. It's nice to sit and home and play in your spare time, not try and learn it three days a month when actually shooting.
