Never say never. Jet2 planned a more substantial subfleet of A321ceo's from TCX and as mentioned, they have a rather inconvenient 3 as it stands.
Whilst I agree that used 738's do make an awful lot of sense and are probably coming at a very good price with plenty of availability on the second hand market, once newer generation, particularly sharkletted CFM A320/321ceo's start getting retired in larger numbers and the fleet of neo's grows, I can see room for those frames. After all, they do need something more "parkable" for the winter months. The neo's are gonna have to earn their keep.