We have a September 10th update from s4gru.com. (For whatever it is worth) Personally I can live with 3G for now but it will be nice.
Here is the link:
Sprint Marketing Releases a 4G LTE City List where work is under way - Sprint 4G Rollout Updates
Here is the link:
Sprint Marketing Releases a 4G LTE City List where work is under way - Sprint 4G Rollout Updates