A purported "internal Sprint document" is floating around the InterWeb, apparently originating from HowardForums. The image shows Sprint's supposed Q3 '08 New Product roadmap, and is highlighted by the mysterious "MP6950" by HTC, which could be a Touch Dual, Touch Diamond, or even a Touch Pro. The current HTC Touch for Sprint carries the MP6900 model number, so logic would dictate that the 6950 is some sort of successor - I'm guessing Diamond but hoping for Pro. A launch date of September 2 is listed for this one.
Beyond the new HTC, Sprint users can (supposedly) expect these other releases this Summer ... unless this thing is a complete and total hoax ... or it's for real but the launches get pushed back, as often happens:
Check out the original post over on Sprintusers.