Go on strike? sounds a bit extreme, TBH. Dude's 27, finally at the peak of his powers - why would he want to ruin his own career? he was playing 2nd division footy in France till recently, for crying out loud (and he's been repeating ad nauseam that he's thrilled with the PL, happy here, etc).
There's 4 years on his contract. Chances of him going are zero (unless someone comes with crazy money, as in "ze formula"). Next year looks almost as secure (but a lot can happen in a year - including us having other CBs?)
Which brings us (and the formula 🙂) to the crucial point in 2 years time. Le man god will have to decide then for an extension' or Tim's suggestion will be a reality (and "decent" then is only about 15 mill, assuming he keeps his top level).