ATR could push up speed, ceiling and capacity on the ATR's a bit. New suitable engines were under development.
They have been discussing for a decade, little competition and -600 success made them shy of the investment I guess.
Wouldn't jet powered aircraft be better? So develop a new wing, with higher sweep / higher flight speed for the regional jet. This could be offered besides the ATR turboprops. The turbo props for short and STOL flights and the jets for longer range flights.
If they keep the same fuselage, possibly they could use the same assembly line. This would be like the Do328(jet) or An140 / An-148/-158.
I think that however scope clause develops. So if it stays or if it goes. There will be demand for smaller aircraft. And developing light weight regional aircraft will make them more (fuel) efficient. So for me the scope clause isn't really relevant. I'm more interested in how industry could develop more efficient regional (50-100 seat) aircraft.
I don't get why development of a new regional jet would be prohibitively expensive, while there are three families of large busness jets being offered (Falcon, Global and Gulfstream Gxx0). What is the big difference that prohibits the development of a new scope compliant regional jet (family)?
AFAIK the PW1000G is actually three different sizes of engine. The PW1200G/PW1700G has little commonality with the other members because it's thrust output is so much smaller. The PW1000G have had problems on the A320 and A220, AFAIK they have been overcome. But these engine problems have lowered orders. I think the PW1200G/1700G is actually still to strong for regional jets.
No other engine manufacturer has offered a new generation engine for regional aircraft. I think this has been the main problem.
I think Bombardier realized that the PW1200G wouldn't work on the CRJs within scope clause. MRJ and Embraer thought they could work it out.
Possibly the higher compression ratio core technologie needs to mature, and ceramic brisk and CFPR fan blade and casing technology needs to mature before engine manufacturers can offer a good engine for regional jets. Is the problem engine reliability and spare part availability?
I don't know if P&W has weight reduction technology available to reduce engine weight of the PW1200G/PW1700G, or if it would be beter to offer PW812 / PW814 for regional aircraft. Possibly RR could make a regional jet version of the Pearl, or GE a version of the Passport (a CF34 successor).