Nobbel does a great coverage of the 6.1 -> 6.2 speculation.
What we know:
- Iron Docks quest hub area is planned to open in 6.2. I envision this happening a lot like Pandaria: Isle of Conquest where we quested to open up the different phases of the island. Instead we'll be headed to Tannan jungle to work there.
- We need to continue the legendary quest chain.. So some new content to generate things to collect. This could be simply something to finalize the ring.
- Blizzcon is November 6/7.
- 6.2 will drop before Blizzcon.. I say sometime around August. It will probably be a two parter as we've seen with Highmaul -> Blackrock Foundry. That way Blizz can announce, part 2 at Blizzcon as well.
- Blizzcon will announce the next expansion. As we're likely to only have 2-3 patches in this expansion, here's to hoping that the next expac drops around February 2016.