Ha-ha, I just found out the Swedish title for Late Night and I don't know if it's official but it makes me laugh. "Kvällsnöjen", it would translate to "Evening/night Pleasures" or "Evening/Night Entertainment". Sounds like the name of some entertainment magazine!
Oh, and the article said something about going to parties,
concerts and
night clubs.
That confused me a bit; we can already go to concerts (well, kind of) in Sims 3 but will there some new kind of concerts in Late Nights? Hmm, they seem to be developing more on the theme of music in Sims 3 so I hope we get something like watching your sim's favorite band or singer in concert. And night clubs sound incredibly interesting, hopefully you'll be able to have night clubs on community lots and such, and actually being night clubs and not just buildings on community lots.
But then again, the article may be misleading on that.
Another note; in the tiny interview with Grant Rodiek they had, he said (I quote, translated to English from Swedish): "[...] But instead of just giving the players downtown hang-outs and things they've seen before, we give them a possibility to go out into the night
with their band, become a cool bartender, a supernatural creature or a real casanova". Source of article is the Swedish gaming website FZ.