The X34 is planned to go every 20 minutes at some point this year, for which these 6 E400s have arrived to work. 19194/6/7 will return to Newcastle once 3 of the 6 new ones are ready for service. If the X34 frequency increase doesn't happen, what happens with the other 3 is not known.
As for the cascades as a result of 37301-19, I don't know the exact details but I think I can safely say Stockton and Walkergate aren't in any of these cascade plans
