Forcing? No.

Attracting regional services by flying flashy DC-9 sized jets for wages 50% less than the DC-9 guys make? Absolutely.

Management will always look for a way to off load wages and costs to increase net profit. You're a fool if you believe that regionals haven't given mainline management a reason to not hire 190 or 737 pilots/aircraft or use -900's as leverage in pay negotiations with mainline pilots.