I predicted a little while back that Vettel would retire at the end of this season, and Monza hasn't done anything to change my mind
. He is only prepared to be a No 1. That's what he thought he had (well, officially it's what he did have) at Ferrari at the beginning of this year, but Leclerc's skills and his own mistakes have determined otherwise. He left Red Bull because he felt threatened by Riciardo so he's unlikely to return there alongside Verstappen (unless his pension pot is not sufficiently full yet). He's not a Kimi; he won't go to a lesser team for the fun of it.
So Ferrari need another driver for 2020. On the face of it Riciardo would be a good choice but he is generally thought to have left Red Bull because Verstappen was putting him in the shadows. Why would he want to go up alongside Leclerc? ItIsI is doing fantastic things this year but he is still inexperienced (measured by F1 races started) so it may be too early to bring in another inexperienced driver underneath him. Raikkonen has been prepared to be a No 2 before and he would be a safe (and popular) pair of hands.
What will Red Bull do? It's early days but Albon is looking OK. If he can keep it up and get rid of the odd lacklustre moment, he will make an excellent 2020 No 2 and the problem is solved. If not, Red Bull will be scratching around to find someone while Toro Rosso will be trying to fit three drivers into two seats. I would quite like to see the Hulk get the seat if they push Albon back out, but he may not be prepared to wait until the end of the year for a decision. At least, not if another opportunity like Haas is open to him.