FWD, 1.8L Juke Turbo powered Altima coupe will get my money as Nissan's next "entry" level sports car under the next gen Z and GT-R. And will probably be their answer to the FR-S/BRZ.
I highly doubt Nissan will release another RWD platform in addition to the 370Z/G37 & GT-R platforms unless it shared chassis with another model. Nissan is pushing the 2013 Altima sedan hardcore right now and are putting off the redesigned Altima coupe models for a little while.