In the same way I predicted Cata's timeline and everyone called me crazy, I'm going to take a shot at MoP's first half year or so. Just for fun predictions, and I honestly don't care what they said about what patch 5.1 is, or 5.2, because unless it's confirmed, it's all up in the air. Still wishing for that WotA raid, Path of the Titans, and Wintergrasp flying. If Blizzard said "oh 5.1 will be dungeons, 5.2 will be raids, 5.3 will be dungeons, because we love giving you guys content," I don't care. Because it's not true until you see it in blue.
2013 Q1 - Patch 5.1 - 2-3 5man dungeons will be released. T14 is a giant tier, many more bosses than there usually are. Blizzard will let players play with t14 for a long time because they know they can, so around late February or early march, patch 5.1 will bring new 5 man dungeons.
2013 Q2 - Patch 5.2 - t15 raid. No idea what this will be, but it'll be a raid. Might be Trolls. Less than 10 bosses. Around late May or early June.
After that, it gets hard to guess. I don't want to try to predict Q3 and Q4, but I would say Patch 5.3 will be the t16 raid, and it'll probably be released in late November.
Edit: Adding a bit more explanation to my guesses. Blizzard works around their quarterly updates. They always want to look good in the reports, while releasing as little as they can. The expansion will carry Q3. They don't need to release anything before Q4 ends because of the initial burst from the expansion, which will still carry on a bit, even if they lose some. Right before Q1 ends, they will release the 5mans, so those who got tired of the expansion already will resub. Then before the end of Q2, right when people are sick of the giant tier, a new tier will come out.