Apple discloses iPhone unit sales, and both AT&T and Verizon Wireless disclose iPhone activations on their networks. So it’s pretty elementary to work out that since AT&T and VZW between them sold 5.9m iPhones in the June quarter, 71% of iPhone unit sales in the June quarter were outside the USA (14.4m units out of 20.3m in total). Indeed, this is where most of the growth is coming from, in large part simply by expanding distribution (most obviously into China).
That means that the iPhone 5 is not going to have features that are only relevant in the USA, especially if they’re expensive and have effects on size or battery life. So, no LTE.
It also points strongly against too-clever-by-half things like soft SIMs, since these would only work on networks with which Apple has spent time and effort doing a special deal and most mobile operators hate the idea anyway. Soft SIM equals less distribution, and Apple is all about more distribution.