The season will not completely end at that point, however. The Arenas will continue, and you will still be able to gain rating and arena points right up until the release of Wrath of the Lich King so you can finish getting whatever pieces of gear you'd like to take with you into Northrend.
I think we all knew they were going to do something along those lines. If they didn't, the entire season would essentially have been blown. Turning class balance upside down and adding a whole ton of new abilities to the game right at the end of a competition is just a poor move. I think this is the best compromise, too. Ending the season while still letting people gear up for Wrath is great. Raid zones aren't shutting down with 3.0.2, so it would be a little annoying for PvPers if the arena did.