I am sure a lot of folks have been wondering what happened to the Fx 1.5.0.X to 2.0.0.X Major Update feature. Many people thought it would be included with the Fx 188.8.131.52 build as that was released a couple months after 2.0 came out in October. Then there were rumors it would be in the 184.108.40.206 build giving users the option to go directly to the 220.127.116.11 build.
After some hunting around (was actually looking for info on the upcoming 18.104.22.168/22.214.171.124 releases) I came across some information about the Major Update. For the most part, the Major Update is done, but still needs to be tested. However the testing can not be done until after Fx 126.96.36.199/188.8.131.52 are released. Once those releases are out then they expect to have the Major Update feature in another week or two which would put it towards the end of February.
News Source: Mozilla Wiki >> Major Update