Just one reason among many why there won't be "the great pilot shortage":

Regionals can't or won't provide a good enough compensation package to recruit & retain enough pilots to meet their CPA performance obligations. After a few months of crew-related cancellations, mainline carriers will shrink and/or terminate those CPAs as allowed per terms of their agreements. RJs will be parked at a rate far greater than mainline adds new, larger airframes.

Total number of regional airframes shrinks, total number of mainline airframes goes up marginally, total number of pilots required remains more or less the same.