https://www.oig.dot.gov/library-item/38120. Here is the link to the DOT's evaluation into the FAA. I hope this is helpful.
That has nothing to do with the issue at hand. It is directed only at improving the identification of airline pilots with mental problems so they can be removed from duty before they do something crazy, like the Germanwings or Egyptajr crashes. Sport Pilot limitations are not part of that effort.
As to a DoT review of the limitations on Sport Pilots, I have not heard of such. Can you point me to where you here about that? I know the FAA is considering expanding the size of the airplanes which Sport Pilots can fly to include things like a Cessna 150 and possibly a Cessna 172, but I did not know of any such review at the DoT level. That said, the FAA review has been ongoing for sometime, and I wouldn't count on it happening any time soon -- major changes in such regulations usually take a few years from the initial idea to a new rule becoming effective.
For a lot more about Sport Pilot, see:
As for being "limited in hours of flight," I'm not sure what you mean. Yes, Sport Pilots have limitations on the aircraft they may fly (mainly size and speed), and the conditions in which they may fly (daytime with good weather), but outside of those, you can fly all you want.