The next NSX needs to be a modification of the RL platform. It can have the Frame turned 180, primarily RWD, with SH-AWD, rear/mid engine layout, and have 2 seater approach. The Wheelbase would grow about 10 inches make the change over to the new platform, with a slight increase in track by 2-3 inches.
The 3.5 V6 should be the base engine, as the option engine should be a V8. Many have hinted at the possibility of taking the TSX/RSX 2.4 I4 and making it a V8 by sharing a common crank, putting displacement in the 4.4-4.8 liter range. HP could go easily upto 480hp with a redline of 8,000 rpm. It can also be produced to provide great low end torque for the Pilot/Ridgeline and even the RL or rumored LS competitor.
Looking at the competition, this seems to be the best answer. Problems:
1) The RL platform would require some re-engineering. Making the Rear axles steer (if spun 180) require more clearance then is available. The Mid Engline layout would require having Rear Transaxle layout.
2) This platfrom was only designed around the 3.5V6 and the V8 would not fit right in. Rumors of the Ford designed Yamaha V8 (used in the Volvo currently) would fit in a transverse fit, but its capacity and output don't match Honda's V8 range of use they are hoping for.
3) Weight. The current RL weighs in at 4000lbs. The ideal curb weight of the Next Gen V6 would be 3200lbs. 800lbs could be saved, but alot of aluminum would need to be used, along with smart reengineering.
4) Cost. The Porsche 911 would be the target. Its MSRP of a V6 version doing about 320hp is $72,000. Seeing as many options seem standard on an Acura besides Navigation, one could assume a base price for a well equipped NSX would be $78,000. Navigation would be a $2000 option.
5) Performance. The NSX V8 should also compete with the Porsche Turbo, with 480hp but do so not to beat it, but match its performance at a lower price with a better build. $100,000 should be the idea for the NSX V8.
6) Leave the possibility of an NSX-R model with very low build counts (ie 100 a year) that might have the indy based V10 or Twin Turbos on the V8 (the I4 already has a turbo in the RDX) that could do 600hp and match a Murcielago, F430 Challenge, and GT3 at the tag of $150,000... Something to bring the prestige to the NSX, but allowing the lower entry models.
I know Lotus was considering borrowing technology from the I4 tobuild their own V8, but chose to use BMWs 4.8 V8 in their new Esprit. They also looked at the RL platform as a donor to a possible Mid Engine layout, but used their own Fleixible Frame Foundation to make the Esprit.
Question is, I don't think Honda will put this much thought into it, because the current NSX is such a slow seller. They would need an instant success which they fear won't happend just based of previous NSX sales. But they only need to look at the RL to judge its success... and shortfalls (lack of a V8)
...
JMO