Revised scenario (at the start of this weekend):
Confirmed:
1. Mercedes (Hamilton, Bottas)
2. Vettel at Ferrari
3. Red Bull (Verstappen, Sainz)
4. Renault (Hulkenberg, Ricciardo)
5. Sainz to McLaren
Pretty certain:
1. Kimi stays at Ferrari
2. Force India (Perez, Stroll)
3. Ericson at Sauber
4. Sirotkin stays at Williams
Available seats:
1. One McLaren seat: Ocon? Norris? Vandoorne?
2. Haas #1 seat: Ocon?, Leclerc? or Grosjean?
3. Haas #2 seat: Magnussen? (option for 2019, has not been exercised yet)
4. Williams #1 seat: Another paying Russian driver?, Kubica?, Ocon?
5. Sauber #1 seat: Giovinazzi or Leclerc
6. Toro Rosso #1: Hartley or someone in the Red Bull system?, Kvyat?
7. Toro Rosso #2: Ticktum?
Adrift:
1. Ocon
2. Grosjean?
3. Vandoorne?
I gather Leclerc is going to have a seat at either Sauber or Haas, so is in no danger. That leaves only the one McLaren seat and one or two Haas seats for Ocon, Grosjean, Vandoorne, Norris and Magnussen. Almost certainly Vandoorne is out. I gather the other Williams seat needs to come with at least $8 million or more. As it is a Mercedes team, it could be a place to store Ocon for a season.
Anyhow, Haas is in a pretty good situation as I gather they may be able to choose between Ocon, Leclerc, Grosjean and Magnussen.