It makes sense if they want to preserve his value. It wouldn't surprise me to see him sign a new contact and leave on loan with no obligation to buy. I think Bellerin has enough respect and love for this club to not run down his contract. I think a deal has probably been agreed to let him leave on a loan if he extends his contract.
If its a year extension then maybe that's a possibility. Hector seems like one of the best characters at Arsenal with real integrity so I could see him agreeing to that possibly although it seems a bit unlikely.