If you enjoy stock Android, want the latest and greatest OS as soon as it is released, and tend to favor software over hardware, then you may want to wait to see more about the next Nexus. However, if you prefer cutting edge hardware, I wouldn't be overly optimistic (you may still want to wait though). From early leaks, the Nexus may only have a 2300mah battery. I'm sure it'll be enough to get through a day for most users, but I wouldn't expect to have the same battery life as the G2. I'm betting there will also be some other hardware cutbacks. Possibly the camera, or maybe the screen. It's impossible to say, but the Nexus has always come with slightly less than top-of-the-line hardware and I personally don't see that changing yet if ever. Nexus devices are not carrier subsidized so Google has preferred to keep the price affordable.
I too considered waiting to find out more about the Nexus, but once the details of the G2 were released I took the plunge, and I've been thoroughly satisfied. Screen, battery life, camera and speed. It hasn't been often that Android has nailed all four of those on one device.