This forecast also says that oil will climb only as high as $104 by the year 2030...not sure if I buy that one.

These sorts of government forecasts are generally limited in that they are politically constrained to not deliver significant bad news and create potential problems for the political masters.

What you really want to look at with regard to 50-seaters is "tail risk"...if your leases end at about the same time as (or before) your feed contracts, then you can dumb the 50's and offer larger airplanes at contract renewal time.

But anybody who has numerous 50-seaters with lots of tail risk is in potential trouble...it would make the most sense for mainline to not renew, let such a regional liquidate, and then contract with another regional for larger airplanes. Better to start clean than deal with a company which has to financially carry the burden of a lot of parked airplanes.