2010: After Chael Sonnen defeated Marquardt by UD, Anderson Silva won by first round KO against Demian Maia. That led to Chael Sonnen getting a title shot in which he unfortunately lost to Silva by third-round TKO.
2011: Anderson Silva does one last fight before retiring, maybe against somebody like GSP, but the result is unrelated. Point is, Silva is no longer in the division.
Vitor Belfort wins by third-round TKO against Sonnen. Sonnen's stamina is what is keeping him from being champ. Demian Maia climbs back up the ladder by easily submitting Yushin Okami in the second round.
2012: Nate Marquardt rematches Demian Maia and wins by UD. It is now clear that Maia has large difficulties fighting any top-notch fighter. Wanderlei Silva has meanwhile been racking in the wins and fights Vitor Belfort, making a much needed win in the second round by TKO.
Wanderlei Silva fights Demian Maia and wins by a unanimous decision to earn a title shot in 2013.
At the end of the year Marquardt is the one holding the title, and Wanderlei is set to have the next shot.
Explanation for decisions: In the middleweight division, Silva has been clear No. 1 for a very long time. Nobody could challenge him, but once he retired, there were so many people all close to equal behind Silva that it became a desperate fight for the top spot, and nobody could hold the belt for long.
If I had to continue the years in the division, I would have Wanderlei taking the belt from Marquardt, and the chaos continues. Most likely a fighter relatively unknown to us now will eventually climb his way to No. 1 and stay there as the new king of the middleweight division.