This early news of Dylan in South America makes no mention of MK:-
http://www.entradasyconciertos.com/2012/01/24/bob-dylan-en-argentina-2012/It is a very premature report, clearly, but one might have expected a reference to MK if it were to be a co-tour of any kind.
Whenever the possibilty of a joint BD/MK in 2012 has come up in conversation with my various contacts, it has always been in terms of a BD/MK tour happening this coming autumn, not earlier. I have taken this to mean that, at this stage, they and their management teams have agreed to keep a run of specific weeks clear in their work schedules and have spoken to the band memebers and the road crew accordingly. Meanwhile, the backroom people will begin to try and put something together. Of course, the principals could change their minds or they might receive an even better offer. On the Dylan side, he likes to finish tours and be home (presumably with the family) by Thanksgiving. Thus, to my mind, "autumn" means the month or so preceding this.
I'm prepared to be wrong but that's my reading of the situation.