This is an impossible question to answer until the next Nexus is released. These devices almost always look awesome on paper, but as we all know, things can change once the they get into people's hands. I'd say only people who are REALLY into the Nexus line and the pure Google experience should hold out for it, assuming they also consider the E4GT to be a great device.
If the next Nexus blows the doors off the E4GT, I'll consider paying full retail and drop my Epic Touch on Craig's List, but I'm loving the phone and there's no way I'm going to return it for something that is currently in vaporware status.
I agree 100% JayWill