Last adult comedy?

what about the Wes Anderson ones?

Well humor is subjective so what's considered intelligent would likely vary from person to person. You could also argue any comedy rated R is made for adults and if so then something like The Hangover would qualify. But I'm guessing you mean something that's more along the lines of a dramedy with almost equal elements of both comedy and drama. Thinking along those lines I'd say Little Miss Sunshine was a great comedy made with more of an adult audience in mind (and released 2 years after Sideways).

Woody Allen still makes mature comedies.

and so does Noah Baumbach.

Considering all of the crappy movies, this Sideways was great!

The Nice Guys (2016) was pretty funny.
Not as good as Sideways though.

Possibly.