It appears on Addleshaw Goddard's website they are still advertising for 2013 TC's. There is a choice between 2013 and 2014 on their website. I assume if you apply for 2013 and there are little or few places available, they themselves will automatically place you onto the 2014 selection?
I think it is very unlikely. They will have a fresh batch of applicants for 2014 next year, and will have a lot more applicants than places. It will probably be a case of giving you an offer if they like you and think you are good enough.