I'd never call anything a slam dunk, but the evidence released so far seems to prove the elements of the crime at least for statutory rape. TC admitted to his wife on the phone that he had sex with ET. Also I remember the people from the CA commune saying they heard TC and ET. I think even without a testifying witness you'd have solid physical and first-person testimonial evidence to prove some of the charges.
It's definitely possible that he manages to plead the charges down to something that no one is happy with. I don't want to get anyone's hopes up even if I strongly believe the facts meet the elements.
IIRC correctly, his wife did not say that he admitted to having sex, she said he admitted to sleeping with her. (Clinton type word games iykwim, but they are two different things. Yeah, we can all infer he "meant" sex, but she did not relay that he said that specific word - and we have seen how such delineations are used by defense lawyers in previous cases)