Depends on the business, man. Some companies are cheap and/or put little emphasis on IT. I've recently seen networks with cat 5 (not 5e) running windows 95 workstations.
As for NEW installations you are pretty likely to see 6 or 5e, maybe 6a soon (though I've yet to). It all depends on cost and what the client actually needs. Cat 5e can run gigabit speed in theory and is more than enough for the needs of many small businesses.