UPDATE: Cinematical was contacted by Penn's rep a little while ago, and informed that Zak is NOT writing Captain America. The wording in the interview made it sound that way (and the transcript was correct), but Penn was actually talking about being attached to The Avengers, not Captain America. Obviously this probably means David Self's script is still in the mix, and we'll update you when there's more info.
In a new interview over at ComicMix, writer-director Zak Penn talked up a ton of projects including his latest film The Grand (which I loved, and which you should see), as well as his geeky comic-related screenwriting projects like The Avengers, that X-Men spinoff flick (featuring the young X-Men), The Incredible Hulk, a new one called Bermuda Triangle and, finally ... Captain America? Oh yes, though he doesn't go into much detail (aside from saying he's attached), apparently Zak Penn is now the guy writing Captain America. (Not sure what happened to David Self?) And assuming Edward Norton doesn't sign on to star, Penn's final script may actually make it before cameras this time.
As far as The Avengers goes, Penn admits they're waiting for other Marvel characters to debut their solo films first, like Iron Man, The Incredible Hulk, Thor, and they may even wait for Captain America as well. So with all those films still left to go before cameras, I'd get used to waiting ... patiently. Penn also talked up the X-Men spinoff story he's still attached to write and also direct; he says it involves "a younger group of X-Men at the beginning" and that "it's a little bit more of getting back to the classic X-Men." No word on when that will see the light of day.
It's good to see Penn is writing Captain America, because if he's the guy penning that Avenges movie, you'd like to see him involved in as many of these as possible. Of course, I'd like to hope he'll find time to stuff in another tiny mock like The Grand, if only to see which ridiculous character he has Werner Herzog play this time.