I think Pelle is trying to get rid of him because he sees him as a player in the stands.
He will put Garcia and Rodwell and Milner ad even Nasri on the bench many times ( or instead one of them Navas), no need for Barry there.
Clearly a fullback or even both will be on the bench (like Zabba/Clichy starts, so Micah/Kolarov on bench).
Pantilimon as well.
And two of Jovetic, Agüero, Dzeko, Negredo.
I expect a few players in the stands vs Newcastle could be a few surprise players being not even on the bench as we have not many injuries luckily now.
Barry's only role could be this season coming off the bench for last 15-20 minutes to hold the lead, make sure we are safe in the back but thats probably not the mentality of Pellegrini, more like Mancini. (Bring off a striker for Barry...)
Also he could be OK for vs. weaker teams only if they dont have pace in midfield but most of the PL teams has pace there and Barry would just struggle.
Also we are looking to press a lot, and Barry cant even run when we have possession he cant run and press opponent when we dont have the ball all the time.
So pretty sure Pellegrini has many reasons not to keep him and there is the financial side also, at least 5 m wages for him and then he could leave free next season.
Given the fact Pellegrini doesnt fancy him at all, its a good decision to sell him now and maybe get a small fee for him as well as save his wages.
Mancini wanted a strong midfielder last year too, like De Rossi who would easily put Barry on the bench for most matches, we only got Garcia so Barry's chances were always going to be limited.