The 18th is only 27 days from the Galaxy Nexus and LG Viper release, so the timeframe between releases of each respective superphone is still likely the same.
That said, I don't know if Sprint really has the earnings to warrant releasing more devices ala Verizon or ATT. I'd love the options, but I don't know if Sprint can justify the costs behind that.
If we were to take an average 30 day timeframe between superphones and the LTEvo is actually released in May, maybe there's another superphone being thrown into the mix. Based on the rumors, this would be my new guess:
May 18 - LTEvo
June 15 - E4GT 2 (aka sgs 3)
July 13 - MoPhoQ
Aug 10 - Samsung Galaxy Note
Sep 7 - New device?
At least, this is how I hope it happens because I'll be able to decide on a phone by the time the MoPhoQ is released.
I think that's pretty good guess.
I think the S3 will be out much sooner this time around probably by middle Summer.
Photon 2 by August
New version of Galaxy Note by Middle September
Iphone 5 October