I can confirm that this is in the works. They are hoping for a July release, but its probably more like September. Sprint ptt is packets of recorded voice streamed through a specific protocol that is then bridged to the old Nextel network, if you're talking to a Nextel subscriber, so technically any cdma sprint phone will be able to have that feature; no longerrequiring you to choose a nasty ass phone just because you use ptt/direct connect.
Long story short, dont hold your breath. yes its in the works, but there's no release date yet.
I am about to get the Motorola Admiral, which is using the newer tech that they are modding into an app, so perhaps after I root it I can perform a "dump" and post it for a dev to look at and see if they can port it over for other devices. It would require the service to be activated on the device, so I'm not sure how that would work, since the PTT packets are different than regular Data packets and are not transmitted on all networks.