I agree with Grits, I think Raikkonen doesn’t know what he is doing. His motivation for a comeback may not really be driven by lust for racing in F1.
I never fully understood why Raikkonen left F1 in the first place. But I understand that he was discouraged to continue because he didn’t really like the idea of leaving Ferrari (hence why he did not like the idea of moving into a slower team). Ferrari were desperate to offer seat to Alonso and best way for them to do that was the keep Massa.
If he does come back im sure he will do an ok job, but i doubt he will have the motivation or the patience to work on car development, testing, traveling etc etc..
It is hard to compare to Schumacher situation. Schumacher went up against Rosberg who is exceptionally quick, and there were lot of changes introduced to the cars since his retirement. But im certain Schumacher will be improving and he will not be leaving until he achieves some level of success …