Our plan for Saliba probably depends on Champions League qualification, and Arteta probably isn't spending too much time making friends with Saliba right now because his main focus is … Champions League qualification.
There are a number of indeterminates in there so it's reasonable if certain things aren't yet decided and communicated.
About a month ago there was a flurry of reports that Arteta wanted to extend Saliba in the summer, I don't know if they hold water either. If that were the case we could extend him and still leave him on loan, or bring him back, depending on what the player was willing to accept of course.
Don't mean to completely dismiss the concerns, but you could write this kind of report about half the players in the squad. "Granit Xhaka has not been advised of Arsenal's plan for him next season", "Lacazette in the dark about Arsenal future and has reportedly never had a pint with Vinai Venkatesham" …