The latest expectation is that the 2016 TSRGD will be published in April to come into force in May.
I’m not sure that it will solve the problem of appeals though. If drivers consider current signs to be too complicated and adjudicators agree, that is not likely to change, as all currently legal signs are intended to still be prescribed in the new regs, plus there is a lot of flexibility to create even more complicated ones. It may help with signs that are clear, but have some minor issue of detail or layout that makes them technically non-prescribed.
And, no, there are no plans for any special training of adjudicators in the new regs. They are intended to just read it as necessary, when it becomes relevant to an appeal.