You would have thought any infrastructure changes would have been programmed at the time the 197s were ordered.
At the moment, Bangor benefits from a weekday roughly hourly service from TfW of 18 trains towards Chester, 7 to Cardiff, 6 to Birmingham via Salop, 2 to Manchester Airport, 1 Crewe, 1 Junction and 1 Salop. It can be assumed the last three are really stock movements. This pattern is augmented by 6 Avanti services - 5 Euston, 1 Birmingham via Crewe.
From what the TfW spin has been, Llandudno loses the roughly hourly service to Manchester and benefits from an hourly Lime Street service which is actually the Chester/Lime Street extended. So Bangor gets one extra through service per hour towards Chester.
So no real benefit for Llandudno unless you want to go to Lime Street instead!