Sprint has a ton of great devices in the fire right now. Most of which are due out this year - or 1Q next year.
Palm is rumored to be bringing an updated Pre (hopefully more than the Plus) to Sprint 4Q this year or 1Q next year. Palm is still feeling a bit burned by the first agreement and blames Sprint for the poor launch - saying if they could have had a bigger push it would have been bigger than the Moto Droid (seriously?) but I think they know where home is and they want to reward the early adopters with an upgrade.
BlackBerry all but announced that the 9650 is coming to Sprint and they just launched the 8530 (updated Curve). Up on the rumor mill from RIM for Sprint is the 9930 - that goofy touchscreen/slider deal that CrackBerry, BGR and Engadget are all saying is going to be an exclusive to Sprint. In addition to those, RIM should also bring the 9130 (new Pearl) to both VZW and Sprint after it is officially launched. The only thing missing from Sprint's lineup is a 9500 series (Storm) device or maybe a 9700 series (Bold) device.
Samsung is supposed to be updating the Moment platform as well to the 1Ghz Hummingbird series processor. It will also feature 2.1 or better at launch, a DTV chip for on device OTA TV watching and a larger base memory - rumors are 512MB RAM / 2GB ROM. Rumor has it that it may feature the Super AMOLED screen as well.
The Hero 2 (Legend) is coming sooner than later as well. I think Sprint has learned not to announce a device until their stock of current handsets is depleted. It will probably just be another modified version of the Legend itself like the Hero was from the original.
Add the Evo into this lineup and you can see that 2010/2011 has a lot of good devices that are coming - both announced and rumored.