Techcrunch's source says that Verizon is "racing" to put up its 4G LTE service in a "bunch of markets" in time for Q1 2010, which is about when both the Verizon iPhone and Apple Tablet are both rumored to hit.
The latest anyone's heard, Verizon's rolling out 20-30 markets by 2H 2010, but TC's saying that the company is rushing a lot of these up into Q1. What makes this LTE-capable iPhone interesting is that both Verizon and AT&T will be moving onto that technology, making Apple's life easier since they only have to make one type of device for both networks. (The fact that they don't need to make a CDMA iPhone just for Verizon and no other service makes this rumor make even more sense.)
There's also talk of data-only plans for this supposed Verizon/Apple tablet, which would fall outside of whatever exclusivity AT&T has with the iPhone. [Techcrunch]