Starting at noon on Wednesday, November 7th, advance tickets for The Hobbit: An Unexpected Journey will go on sale in the United States. In addition some theaters will have The Lord of the Rings Extended Edition Trilogy marathon on Saturday, December 8th and Sunday, December 9th.
On the format front, things remain confusing but Regal Theaters provided some clarity by saying that their 48 frames per second will be in 3D only or what they label as "HFR 3D". Still this leaves 2D at 24fps, 3D at 24fps and 48fps, IMAX at unknown fps, IMAX 3D at unknown fps and that is before you Dolby Atmos to the equation.
To simplify, if you goal is to watch it the way Peter Jackson wants you too then you want 3D IMAX at 48fps in Dolby Atmos. If you want to remain consistent to the Lord of the Rings trilogy (my preference if only to avoid the format headaches) then stick with traditional 2D at 24fps that most theaters will have and how have been watching movies your entire life.