I was actually recently put into the same situation. A couple friends from a guild I raided with for years informed me that the guild had fallen apart and basically all of my close friends, people I stayed in touch with on steam and facebook and LoL after quitting WoW, were forming their own, new 10-m raiding guild and wanted me back.
I'm actually going to tell them no. Pandaria, iunno, it killed WoW for me. I'd been playing since vanilla and hadn't had more than a couple 3 or 4 month long breaks in that time. Heading into Pandaria, after all that time, it was just too much of the same. Too much grind, too much annoying pvp, way too many dailies, and basically the same raiding structure. I gave it a good go, and who knows, eventually I might go back, but in my opinion, not enough was actually changed in Pandaria to make it worth going back for if you were already bored in Cata. But of course, this is also the internet, where everything is opinion! If you want to go back, GO! Make your own opinions and decisions based on your experience in Pandaria! (It certainly was PRETTY, I'll give it that)