Speculation, in my own humble opinion...
The iPhone 5 is going to release between Early June and Late September. If Sprint wants to lock consumers in, they must release the EVO at least 2 weeks prior to Apple realeasing the new iPhone. Following this logic, and assuming the rumor of it not being released until September is true, then we may all be in for a longer wait than anticipated. However, if the iPhone 5 is going to follow the past 4, then we can expect a release date of the EVO 3D right around the last week of May (at the EARLIEST) to the second week of June (towards the back end of optimal marketing time). If any of this is to be true, then we must expect more news of the EVO 3D to begin floating around within the next 2-3 weeks, FCC clearing in 4-5 weeks, and finalization around the second to last week of May.
However, this is all pure speculation from a marketing standpoint. Feel free to critique this any way you like.