peekay4,
Using recent data from Expressjet, your contention about movement being more attractive to the more junior people is supported:
Year 2014:
seniority < 5 years...42% of those leaving
5 to 10 years...40%
2015 so far:
data almost identical
Of course, the future of the regional airline model in the USA can only be the subject of speculation with some predicting the demise of many of them. We'll see...
And there's a wide variation in how well people progress when comparing one regional to another. But, my source says that, at least at Expressjet, there's a senior cadre that isn't going anywhere. It took my source over two years to just get off reserve as an FO. Other regionals will be different perhaps.
I would venture the opinion that at this moment in history, there's very little risk in going to one of the big US legacies due to monstrous age-65 attrition. This, at a minimum, might function as furlough protection when the inevitable economic downturn happens. As for the risk of a legacy just disappearing like TWA, EAL, BNF, etc., well, what can one say about THAT ?