They'll probably look a lot like they do now.
Remember, I'm from a generation that would watch programs like Battlestar Galactica, Space 1999 and others and figured that by the time I was 30, we'd have spacey-looking cars, jet packs and be colonizing Venus.
2004 is a lot like 1970 but with a lot more telephones and more TV channels.
I gather 2040 will be a lot like 2004, but with smaller telephones and way too many TV channels again.
Unless, of course, someone starts lobbing nukes in the meantime then we'll be chasing one another with "Board with Nail".