If nothing concrete is announced by tomorrow, I'm going to pure order from ATT and drop sprint when it comes in.
Experience tells me that they do this every year, the HTC one was announced first and releases mid April-to end of April. You won't see the GS4 launch because they don't want people returning the brand new HTC one within the 30day period to swap it out for the new GS4. Trust me this was a big deal last year, even I did it. Bought the HTC one 4g LTE and was so disappointed by it's lack of multitasking at the time(don't know if that's been fixed but I sure hope so) that I returned it on the 29th day when the gs3 was released. HTC I would imagine has some deal with Sprint to not even announce the GS4 until the HTC one has a solid leg up. Just my opinion...
i doubt it has anything to do with HTC having a deal with sprint..i would lean more towards your first choice though..they cant piggy back phones kicking out..if they stretch it a lil bit then say 4 new phones getting kicked out over a 4-6 month period would be better for them than unleashing all 4 at once..
they wont kick out any dates until its been announced publicly...until then they dont want any repeats of the EVO LTE debacle. wasnt exaclty something they could have prevented..but they still got the backlash for it though