Bear with me, it's been a long day after a catastrophic server failure at one of our sites. Still attempting data recovery.
The 2016 date has already been published and confirmed for the 2G network. Based on the AMPS project we had to undertake, the sunset date isn't set in stone, but I wouldn't want to find out the hard way that the network support had been stopped before dialer replacement.
Whether or not the service is CDMA or GSM is irrelevent, that's a carrier level issue and determined by the cell dialer/carrier chosen. The majority of units out there presently are 2G, so unless you get a specific 3G unit (few out there) you're going to need to wait a bit for more to come out. Uplink is offering an option to dealers at a higher subscriber cost to subsidize and cover the replacement when it happens, but the overall cost could be banked and put to buying another dialer at the point it's needed, depending on your service carrier's pricing structure.
As far as ideal, with the M1G, at this point, I'd still go with a unit that is serial data compatible over dialer capture as long as that option is available, just because of the nature of the beast.