My understanding is as follows:
Providing the withdrawal agreement is finally passed, licences will continue to be mutually recognised during the transition period. This is currently until 31/12/2020. At that point, there is either a deal, no deal or an extension to the transition period. My GUESS (and it is just that) is that: a deal will probably include ongoing licence recognition, but this is not certain; no deal will almost certainly mean no continuing licence recognition; an extension will mean the mutual recognition continues during the extended withdrawal period, but with ongoing doubt about what happens at the end of transition. If you plan to continue living and driving in Ireland and can live with the category losses, the path of least pain would seem to be to exchange your UK licence to Irish sooner rather than later.
If I was a betting man, I would probably put my 50 cents on the withdrawal agreement clearing the UK parliament (it's already through the Commons) and that the UK toddles off out of the EU via the agreed transition on 31/1/2020. I would not put anything on any of the possible outcomes at 31/12/2020 - it's far too uncertain.
Paul