I think that would be bad timing for a Verizon announcement. Wouldn't that just piss off anyone who signed with AT&T for the iPhone 4 just because they couldn't get it on Verizon?

Besides, if they're going to announce a Verizon phone then they're effectively announcing a new model; the GSM iPhone 4 obviously isn't compatible with Verizon's network. In my opinion this is the kind of thing you'd do at the launch of a new iPhone generation, not just a few weeks afterward.