If the clause would be limited to 2-3 years and we'd have zouma and koulibaly in full force at that point, i dont see him wanting to come back, though...
That is, if we manage to sign koulibaly
It says that chelsea was against the sale for a long time, but conte has come in and wants to buy a new top-class CB from serie A right now, so the club is apparently willing to sell christensen.