Second: Turboprops above 90 PAX lose the benefit in comparison to jets and turboprop engines for above 100 PAX planes do not work any more. This is just physic, please just believe it, it will be pages after pages to explain it in detail (and this I will not do). So, if Embraer will construct a new turboprop, it will be an ATR-42/72 competitor most likely so for the 50 to 90 PAX market.
I do not believe without evidence. Where is the physics?
I know that propellers lose their advantage at longer ranges, but why the size? Is it just the typical correlation between size and range?
Most 737 flights are about 1 hour and at those distances the speed is not yet that decisive. Keep in mind the huge ecological pressure (quite justified, IMO) that may lead to banning short flights in favour of trains. Flying more ecological planes may be the only way so save flying.
Sure there is an engineering gap as PW150 may be too weak and old and civilized Europrop would make sense only for >200 pax propliners, but there should be some incentives to develop a suitable engine.