I agree with IAH. Regional jets were designed to serve small markets, and then got pressed into service on mainline routes.

We will see 50-seaters leaving mainline routes in droves.

As for the small markets, ticket prices will go up dramatically. This will scare away some pax, reducing frequency. If a market cannot support 45 pax per day at the new prices, then service will likely get dropped. The good news is that for many small towns, the only alternatives are to stay home or drive...if you drive, you have to put gas in the car