The current version of the course on edX is the fall 2013 version. The fall 2014 version is expected to be on edX in January. However, you can still access the resources of the fall 2014 version through http://cs50.tv/2014/fall/
Update: if you're able to submit all the psets as well as the final project before December 31, then you should take the fall 2013 version (currently on edX) for an honor code certificate offered by edX.
Otherwise, you have three options:
to keep following the fall 2013 version and maybe submitting as many psets as you can just for practice while waiting for the new version to be on edX.
to follow both versions with the option of submitting the solutions to the psets of the fall 2013 version still on the table.
to follow the 2014 version and wait for it to be on edX so that you can submit the solutions for the psets as well as your final project.
It's worth mentioning that I don't think the new version of the course have way different topics than the current version. Even if you follow the 2013 version, you can still skip the unneeded parts when it comes to the 2014 version. This way you'll probably get use of both versions by learning the basic material as well as learning the additions/differences in the 2014 version. The decision is certainly up to you.