During the Preview Technical Conference the according PM already announced that the Wiki for The New Microsoft Dynamics AX will be opened for the public when the application itself gets into public preview state, too. Until yesterday it was only accessible with a valid user and a password which is not the case anymore so it seems like it just happened!
That means YOU are able to access it already!
The new Help Wiki contains content about development, upgrade, functional topics and is going to be the central of AX content. It also integrates with AX itself so if you are in a sales order, for example, and ask the system for help (as if you would have pressed F1 in AX 2012) the Wiki is one of the sources that provide supportive information to you.
If you wonder why it is called a Wiki – yes, as of the statements made earlier there are plans to let people contribute to it. I’m sure they’ll tell about the plans in detail soon. I can tell you that it is based on WordPress though which comes with a well-known editor and syntax for lots of us (e. g. this blog is based on WordPress, too). Right now it is read only but that shouldn’t keep you from diving into all the information!
Of course everything still is in preview state and might be changed until GA…