Nothing official yet.
Rolling year to the end of September was 2.61m
For the last two months compared to 2017, Paris (Air France), Faro, Lisbon and Luton were gained. Newcastle and Providence were lost. So I suspect it will be around the 2.8m-2.9m mark for the year.
Incidentally, in a sign that the route struggels with capacity in the lean months, Air France aren't flying to Paris on Tuesday and Wednesday in January and February, while Aer Lingus aren't on Tuesday and Saturday in January. Clearly no collusion as there are no Tuesday flights at all, but two flights on Thursdays, which isn't a much busier day.
Not sure where you got that rolling year figure. Rolling year to the end of September was 2,365,567 as per CSO figures. 2.5-2.6M projected for next year (not forgetting one of the daily Heathrows has been axed along with DUS)