Definitely not suggesting we should sell him, presuming the player himself wants to extend his Arsenal contract—wouldn't mind a public statement from him on that front, I don't love it when our own players don't commit themselves.
Should we not have a Champions League campaign next season, the opportunity to rotate and motivate first choice quality centre halves will be less. Under those circumstances it's not obvious to me Saliba should be brought back from loan.
I'm aware there are quite a few people on OMITT convinced Saliba's level is such that he'd walk into our first team, but the partnership between Gabriel and White in central defence is now settled and effective, and there is no pressing reason to disrupt it. It's worth bearing in mind Saliba's a 20 year old of uncertain temperament currently flourishing in a much weaker league than the Prem.
You'd hope we go on to claim a place in the CL and have that extra incentive to bring Saliba back to compete. But given this remains uncertain, it's appropriate if we haven't given Saliba any assurances yet.
In general it's silly to think the competitions and matches players might actually play in shouldn't affect contract and loan planning.