Zenimax has recently removed the option to purchase a 6-month sub to the game, citing that “it wasn’t popular”. Which is a pretty weak explanation, in my opinion. I’ve seen something similar happen, with almost the exact wording, when Warhammer Online was nearing the end. They removed the 6-month option about 6-8 months prior to that game closing.
This leads me to believe that Zenimax is planning a change in payment model once the game is launched on consoles in 2015. My initial thought is it will become similar to DC Universe Online. The base game will be free-to-play and you can reach max level, earn your Champion points since that system will be in place, and participate in any content up to that point (Craglorn, etc.). However, any new content beyond the console release will need to be bought. I think DCUO releases 2-3 DLCs per year.
Lots of discussion and speculation on the forums but Zenimax is tight-lipped for now.