I highly doubt htc cares if they are released around the same time. This isn't an evo 3d vs sensation this is tmobile vs sprint with htc providing the ammo to both sides. Both phones will probably sell like hot cakes so while tmobile and sprint are going at it htc will be reaping the benefits. Also with tmobile and att already having a dual core phone out in addition to verizon releasing the droid x2 in less than two weeks sprint will be the only one without a dual core phone available to the masses. For the sake of a pissing contest between all the carriers I don't see sprint waiting until july to release this phone.
EDIT: Also to add, sprint needs to take advantage of the fact that there is no iphone to talk about at the moment. They need to get people under contract so they don't have people jumping ship come september. Times have changed, phones don't have a shelf life of 2 years anymore. You have to keep your customers interested or they will leave.