If De Bruyne is in form like last year, he would be an asset for Chelsea NOW. But currently, he's a bit out of form and at this moment he's not good enough to help Chelsea. This has many reasons, mainly being Genk's poor performance in the league and him being stressed with all these tranfer speculations. But it doesn't look like Genk is going to have a better second part of the season, so letting him stay at Genk won't help his progression at all. It might hold him back a bit actually. So if Chelsea does buy him, I think the best option is to transfer him immediately. Genk is much less dependant on De Bruyne this season (compared to last season), so I'm confident that with a bit of extra cash it's possible.