The day that Verizon gets the iPhone will be remembered as glorious by everybody who's dropped 12 calls in a row, been taunted by meaningless signal bars and just plain had a miserable AT&T experience. But they shouldn't buy one.
Let's keep in mind what Apple—or rather, Verizon—announced, precisely. A new carrier for the iPhone 4. That's it. Not a new product. That's why Apple ceded the stage to Verizon.
Apple will announce a new iPhone in June, as they have every year since 2008. It'll go on sale later that month, or in early July, as it has every year. That's six months from now. And it'll be better than the iPhone 4 in some tangible way. Maybe not on the order of the leap from the 3GS to the iPhone 4, but it'll have something new to offer. And everybody will want it, because that's how things seem to work with Apple: There's just enough new to make whatever Apple product you've currently got in your hand feel deficient in some way.
But the people who just bought on an iPhone 4 with Verizon will be locked into new 2-year contracts. Their new phones, though maybe better at holding calls better than their AT&T counterparts, will still be old news just a few months after birth. Maybe AT&T will even get mobile hotspots like Verizon, eventually. And what if the iPhone does the same thing to Verizon it did to AT&T? Let everybody else be an early adopter.
It's possible that Verizon will come up with some crazy deal to make its warmed-over iPhone 4 undeniably tempting—unlimited data would be a start, since the phones cost the same as on AT&T. But the only deal you should consider is one that'll let you upgrade to the next iPhone almost immediately, like a one-year contract. I wouldn't count on anything too wild, though, because Verizon is the most conservative carrier of the four—it's got the best combined network and hardware position now, and it knows it. Remember? It's Verizon who passed up the iPhone in the first place, not the other way around.
It's virtually guaranteed that the next iPhone will come to AT&T and Verizon at the same time (there might be some gap, but it will likely be small—after all, Apple doesn't want to hose their 100 million potential new customers). So if you're on Verizon, itching to the pull the trigger, do yourself a favor. Just wait. You've held on for years. What's a few more months?