There’s a plan to build a Cork-Dublin-Belfast high speed (300km/h standard) line, but it seems unlikely to happen. There’s a more feasible-looking plan to upgrade Dublin-Cork to 200km/h (high-ish speed?) via improvements to the existing line (which currently caps out at, at best, 160km/h or so, but much worse in many parts); that seems likely to happen now.
This would bring it from 2h30m to maybe 1hr30, which would be a big improvement. There’s an argument that Ireland just isn’t physically big enough for ‘true’ (TGV/ICE-type) high speed, though I’m not totally convinced by it; with a 300km/h line it’d be less than an hour journey, making commuting borderline feasible.