To answer the initial question in this thread, I doubt that the airlines will purposefully cannibalize their own regionals. But, I think that they will cannibalize each others regionals.

Delta is hiring 120 pilots a month for the next 6+ years. Imagine the damage they would do to an AA WO if Delta were to hire a few hundred from them in a couple months. They could hire every LCA that the WO have in 2 months, or they could hire 25% of all PDT pilots. That would essentially cripple the regional feed of their competitor.