I went to Best Buy today just to at least check out the new 2014 E series and the guy helping me said I think this is a new one pointing to a M, I was excited for about 2 seconds until I saw the "A" at the end and then also read the specs (3D, etc)... Not that i'm blaming the sales guy, the current Vizio's are now coming in the new boxes (as others have pointed out) and the general sales person at a local B&M can't be up to date on every single TV release schedule. Anyway, needless to say nobody there knew when to expect the 2014 sets other than to say they were due some in the next few weeks (E i'm sure).
The only way we could find out for sure would be to have someone from Vizio corporate give us the dates, or like the E series just have it start showing up, news will travel fast. Considering Vizio has all the specs and prices online for the E and M series I would just think the M are due any day now. It's the P and R series that could be toward the end of the year.
I was keeping an eye on Vizio's mean site and ever time they have put a new model out to market there site has been updated. They still are showing the 2013 M's. So that seems to be what they have been doing.