My guess is that OFF2 (P4) will be released sometime between this summer and the end of the year, with it being more likely sooner rather than later.
(The above represents my opinion ONLY and does not represent the views of any of the developers of OFF).
The FM in OFF is very good, but as von Bauer says, it is not perfect. And, if he can teach me how to make the current Dr1 do a flat turn, I'll give him my first born child. The planes do have heft and they will stall, but probably do gain height a tad bit too easily--at least until you get above 12,000-15,000 feet. Lastly, gyroscopic precession is not currently modeled directly, but that is because of the CFS3 influence. Maybe the release after P4 will have a different engine that will allow GP to be better modeled. Finally, from what I have read (I have never played ROF), the damage model in ROF is probably slightly better than P3. But, in all other respects, OFF is superior to ROF, in my opinion. If you truly want the experience of flying a WWI campaign in a living theatre of war, there is no comparison to OFF, with the possible exception of Red Baron 3D.