As long as i am using MPT, i will maintain my own OHM/CHM for the current version, but i will probably always be behind the most recent build of MPT by a few months or even a year, and i will not update unless there are big changes or additional features (such as those coming up in 1.20). I imagine Jojo or someone else will keep the Wiki pages more up-to-date, but he will apply his own filter of what should be included there. The details of MPT (which i call the MPT Reference) will usually not be found in the Wiki version, as this is for quick reference of MPT's usage rather than detailed info on such esoterica as the dialogs, the minutiae of plugin workings, the menu descriptions, etc. As the devs continue to improve or fix MPT, they will generally probably not include all the details of their improvements in the Wiki (altho you'll be able to see what they've done in the version log).
But i agree -- i want to maintain a record of practically anything having to do with MPT, which was my whole purpose in creating the OHM. I want new users to be able to jump right in, intermediate users to figure why they can't get done what they want done, and veteran trackers to understand exactly what's going on with MPT as they try to stretch the limits of its features.
So, it may not find its way to the Wiki, but i will try to maintain it in my OHM or Reference PDF. Of course, as Jojo says, some questions to new users may be too broad to be made "MPT-specific" and should be left to the new user to go find out at other web pages...