Kimi retirement was inevitable, but still, it's sad to see these news. He is legend and one of few old school drivers remaining. I just remind that his debut was 20 years ago, it's such long time for motorsport.
I will really miss his legendary radio converstations.
Now Alonso is last driver from old school and it's great that he is going to stay in F1 for at least one season.
Inevitable that's true, but I would have hoped that we would see him another year, apparently he had already decided in the winter, but the results with the Alfa are not encouraging that one finds the motivation after so long time to drive another year, see Rossi.... There go this year 2 motorsport icons in retirement, the last as you already note is Alonso, think with him will also be next year end, possibly we see in a few years Alonso, Kimi and Rossi at the 24h race of LeMans, I do not think impossible.
I honestly believe that Bottas and Russell should finish the season where they are right now. I get that the need for changes is coming up and Mercedes feels like if they could get George to learn to race with Hamilton which is not an easy thing, then they could have a lot more points which is something they need a lot this year because of how Red Bull is racing, but I believe that they should keep this up. What could happen if they stay like this? Perez is not good at all, so Red Bull would have a winner of drivers cup at the very best case but Mercedes will win constructors cup and at the end of the day we will have a change. Is that really too bad?
I fail to see the reasoning behind rushing George into Mercedes in the middle of the year, with the adaptation process and all that it will take Russell some time to get used to the new car, I do not see a point in that.
It seems that there are no prerequisites for the replacement of Bottas with Russell to take place in the middle of the season, because Mercedes is not Red Bull and Totto Wolf is clearly not a fan of such decisions. However, Red Bull also decided not to arrange shocks, as could be expected judging by past events, and extended Perez in the middle of the season, to which Perez happily slightly squared his car in Spa, giving the Red Bull mechanics an excuse to show their best qualities and have time to fix the car for the delayed start of the race
However, as we know, the race was not much delayed, limiting itself to only a couple of laps behind the safety car. In any case, as far as I remember, Toto Wolf said that the decision on the composition will be made with an eye to the next season
Also think that there will be no driver castling this year, unless Bottas goes to Williams... Red Bull is different, they have 2 teams and the drivers probably clauses to drive in the other team, this possibility has Mercedes probably not so easy, unless Bottas goes to Williams, but I don't think that there will be a change in the current season.