I think word is out that many have been unable to upgrade due to circumstances beyond their control. Off the top of my head, I know people who have been hired at United, US Airways, Spirit, and Virgin America without any turbine PIC time. And as far as I know, they were all just regular line pilots (no special connecrions) who had the good fortune of getting the call. So it does happen.

Obviously, if you do have PIC time I think you're a little more competitive. So if you don't think you're going to lose any money or QOL by bailing on the regionals, then yeah, why not?