For me personally, the most realistic option is he completes his contract and leaves, while we start looking for a potential manager(s) right now. I don't see the point extending it for just one year.
it takes away the whole season being about “is this his last year” constant speculation, every press conference being asked about it and all the focus where it doesn’t need to be. Gives a years run at it even if it does end up being his last year/