With the first bit of season 4 gear
showing up in data mining sessions of the 2.4 patch, there's been some speculation that the season itself might be approaching. However, many people have argued that even if they do implement the gear, season 3 hasn't been around near long enough for it to be time for season 4. Drysc would seem to beg to differ. In a thread on the general forums asking about the start of season 4, Drysc chimed in
to say that seasons will tend to match PvE progression, with upgraded PvP sets to match. He said that with the Sunwell Plateau coming out, more PvP gear and a new season were an inevitability. He also mentioned that there's no set length to arena seasons, and that there's also the possibility of a new season with no new gear.
The idea of new gear for a new tier would make some sense and be in line with previous season debuts. After all, Season 2 coincided very closely with the release of the Black Temple, although there were a few extra weeks between the two, apparently mostly to give people advance warning to finish the race to Gladiator and try to assure the acquisition of a Netherdrake mount.
Of course, he didn't say officially or exactly what was going on, but the implication seems to be that with a new tier of progression in the form of the Sunwell Plateau, we should expect a new PvP season as well. It's not a given, but if you're a gambling type... you might consider saving some of those arena points for the patch.