I think I know where your coming from Pammy'.
When/if parts of the E-jet fleet are replaced by the Q400/ATR/Bristol Box-kite or whatever, what will become of the F/O's, especially those at the bottom of the list?
I still look for Commies' under my bed at night as well. Personally I would imagine these people would progress onto the proposed expanding Virgin Jet fleet? All things being equitable. Unless of course you are suggesting that some Current Virgin Jet F/O's would have their noses out of joint because of lost command opportunities onto a Turb-prop!
All crewing issues, that will need to be sorted as just one aspect of what would be a complex and risky excercise.