Edit: per MMO-Champion, 4.2 may release June 21.
Blizzard has just posted their traditional warning of the end of the current Arena season (season 9).
That means that there are about three or four weeks left in this arena season. If you're still working on your rating, now is the time to pad or protect your position.
A week or two after the season ends we should see patch 4.2, which brings the next raid tier and a new daily hub with an associated faction and faction rewards.
Valor points will convert down to Justice points when the patch goes live, as will Conquest points to Honor points. The current gear available for Valor and Conquest will drop down to be purchasable with Justice and Honor, respectively, so don't worry about losing out. You will have to earn a new pool of points to buy the shiny new stuff though.