Cosby has already admitted to doing what he is accused of in the past.
No, I don't think he did admit to what he's being accused of. He did admit to "having sex on his mind when he bought his drugs" which is different from admitting to raping someone.
Back in my college days I had sex on my mind every time I offered to buy a drink for a cute girl... or even when asking one to dance. That in no way means that I ever intended to rape anyone... but I certainly had sex on my mind.