This is just an opinion--but seriously, look at some the mainline-owned regional carriers--PSA, Horizon, Piedmont, Comair, AE...they all have relatively long upgrades and thus high labor costs. In this day and age of low-time cheap labor and a general trend of outsourcing, those carriers are probably a lot more prone to getting packaged and sold than "mercenary" carriers who have the flexibility to fly for whoever they get contracts with. Eventually a point comes where the higher labor cost margin of running connection flights with 7/5 yr Capt & FO outweighs paying another co. to do that same connection flying with 2 yr Capt/1 yr FO.
In this day and age, I would imagine the mngmt at AA and Delta would want to outsource as much of the risk and price competition of the domestic markets to regional carriers, and focus their mainline operations on lucrative biz travel routes and transcons. I'm not saying that's a good thing for pilots, just saying that a mainline-owned regional doesn't offer the stability it once did.
Now, if any of the above mentioned carriers had flowthroughs that amounted to anything but carrot-waving to get pilots, those companies would be worth the 7 year wait.