The tough thing about the VZ iPhone5 is no one has any idea if or when they will get it. Just because Apple and ATT are on a cycle of a new phone every June/July-ish, that does not guarantee VZ will be getting it at the same time. These are 2 different companies here.
This is the Apple Marketing machine on full blast. They want people to speculate, talk about it, start rumors, and create the buzz for them, all the while leaving us officially in the dark..... wondering.
In your situation since you cannot upgrade until May, you might as well hold off until June/July to see what VZ does. You would be kicking yourself if you bought the 4, and then the next month the 5 did in fact come out on VZ.
Just my 2 cents.