Bitcointalk was the creator for Bitcoin and not Bitcoin created for it, so if Bitcointalk closes down today, Bitcoin will stand.

Bitcointalk is a forum created by the creator of Bitcoin, but after then, it has entered into the limelight beyond what Satoshi Nakamoto created. It has been integrated into the mainstream of the global financial market, with numerous social and traditional media outlets naturally promoting Bitcoin.

Aside from the huge Bitcoin community, governments, individuals, and companies are investing massively in it. So, it can't die just because of a forum.