Depends on which books, and where in his career he was. He got fairly blatant around mid-career, although rarely actually explicit. When they say 'Foundation Series' it's open to interpretation on which books are likely meant - The original three were early in his career, and didn't really have much sex in them. The later two (mid-career) at the end have sex as a major plot driver/enabler, and the two prequels (end-career) feature it without making it a huge point. So it depends somewhat on where they start. I'm betting they'll start with the prequels - they have a strong central character, and can lead into the rest without much issue even after he dies. (And a fair amount of sex if they want it.)
The other point I'd be worried about is violence - the Foundation Series is about the fall of an empire and the rise of a new one, but actual fighting doesn't occur often. There are several places where it looks like it's about to, but then the forces of history make it unnecessary. (Or the populace gets mind-controlled, in one case...) It'd be very tempting for a director of a drama series to ramp up the violence, but it would change a large part of the point of the stories.
Oh, and in response to a couple levels up: They didn't use robots for sex in the stories. They didn't use robots for anything, in fact. There was a complete ban on higher-level AIs and on humanoid machines, to the level of taboo. (Although there were a few characters who where extremely humanoid robots in the prequels and sequels - and were basically the reason for the bans.)