Looks like Arsenal will have Luiz, Gabriel, Saliba as 3 of their centre backs next season. 2 pretty promising but inexperienced centre backs there.
Interesting to see who stays out of Pablo Mari, Chambers, Holding, Mustafi and Sokratis to provide competition. Can't see them keeping all 5 though not sure what type of fee they'd get for any. Suspect Holding might be the easiest to shift but might, alongside Mari, be one of the centre backs they want to keep.
Interesting to see who leaves Arsenal in general. I suspect they'd love to shift Chambers, Sokratis, Mustafi, Elneny, Guendouzi, Ozil if possible. Maybe even Lacazette. Guendouzi is an interesting one since he's a very talented player that it looks like Arsenal have tried to use in swap deals for other players.
You're defo on the right lines. Saliba, Gabriel, Mari & Luiz are the 4 main Centre Backs that you imagine will defo stay. In an idea l world, Arsenal would probably look to shift nearly all the others, but that might be difficult for a variety of reasons.
Sokratis looks the most likely to be off, as Areta doesn't trust him enough to play out from the back. Italian teams have been credited with an interest, Napoli & Roma names mentioned. Mustafi played a bit better under Arteta but they would probably have encouraged him to leave, but he is carrying an injury just now so doubt that will happen.
Chambers & Holding i'm not so sure, As has been mentioned Chambers has attracted interest from Fulham which makes sense seeing he done well for them on loan, but is recovering from an ACL injury so that complicates things. Holding might hold some interest, but nothing serious as of yet.
As for other outgoings, yeah your looking at Elneny, Mkhitaryan & Guendouzi for sure. They'd love to get rid of Ozil but he'll see out his last year. Other potential outs could be Balogun, Kolasniac, Torriera, Maitland Niles, & even Lacazette. I think it all depends on how other sales go.
They'll want to now try & raise money to sign Thomas Partey, so it might take selling 1 of the latter 3 names mentioned above that Arteta might not want to leave but might have to accept to get him. We'll try & get Ceballos on another loan. I think that would be us finished then, bar perhaps an opportunistic deal for someone like Coutinho. I've seen us linked to Auoar, & would love him here, but I just don't think we have the money unless we somehow sell really well, & we rarely do.