As far as I can tell, the initial source for the latest Thibaut Courtois quotes making the Internet rounds is the story carried by Madrid-based Spanish sports daily AS. I've seen them attributed to various other outlets - the Dutch VI is another potential winner - and framed in several different ways implicating for or against a future at either Chelsea or Barcelona, but it seems that the quotes themselves carry no such connotation. Whether either of these two news outlets are the actual original source (rather than, say, a Belgian one) is debatable of course, but it's the best I can find for now.
"I am in my best form. And I feel that I am among the five best goalkeepers in the world. I've grown a lot in the Atleti, especially last season when we won the European Super Cup and the King's Cup. 've made great progress, especially in terms of speed, reflexes and experience.""I want to play, I will not be sitting on the bench. At Atletico I feel great and allows me to play in the Champions [League]"
-Thibaut Courtois; source: AS via Google Translate
Courtois is super talented and he knows it. As such, he doesn't want to sit on the bench, he wants to play. You could take this to mean that he wouldn't want to sit on the Chelsea bench (unsurprisingly), or that he wouldn't want to be second fiddle at Barcelona (unsurprisingly), or that he wouldn't want to not continue being first choice at Atlético Madrid (unsurprisingly). Or any other team on the planet, including probably Belgium, for that matter. He's that confident.
And he's that good.
Since we've talked about this not too recently, let's have ourselves a poll: