This is how I think Sprint will release these phones:
Late May early June: Evo 4g LTE
Late July early Aug: Galaxy S3 (samsung wants worldwide launch and official phone of Olympics it makes sense July/Aug).
September/October: Photon 2 and Iphone 5
That pretty much sums up how sprints been doing it the last couple of years. They leave about 35-45 day gap between big releases.