As
@suey_11 rightly mentioned above, right now it's purely press speculation that is suggesting that Costa's move is nigh on certain to occur.
He's going to be a Champion again, in a team where he plays a pivotal role and under a manager who'll give them a great chance in Europe.
Obviously he may be swayed by the cash of China but will that bring him happiness? Unless it's Atléti calling I'd expect Chelsea to be confident.
If he stays then I'd sincerely doubt Rom would go there to play second fiddle as I sincerely doubt that Conte would accommodate them both.
That only leaves a probable destination of PSG or perhaps Manure, but the latter I feel more unlikely as they aren't getting to get CL football.