Could be one of those merry-go-round types of deals.
Mbappe strikes me as the Real Madrid kind of signing, but so does Salah.
Could Messi still go to Man City? Would they be able to arrange their finances to pay ridiculous wages to both him and Mbappe? Probably.
Haaland will be on the market, although this could wait until the following Summer. He could go to any of PSG, Man City, Liverpool, or Real Madrid IMO. Don't think he's a Barca player or would stay in Germany so not Bayern.
Don't want to stray too off topic, but I do think Mbappe's move could be affected by some of these. Despite Real Madrid's situation, I think they'll be looking at all of Mbappe, Salah & Haaland over the next two years and knowing them they'll probably get two of them.
Definitely don't think any of Liverpool, Man Utd or Chelsea will be in the running for Mbappe. Real Madrid, Man City, or maybe Barcelona but I think even that is a bit of a stretch, would have to lose Messi first and probably find a way to raise some funds even then.