I agree - it's very difficult to predict and possibly will not make any great deal of difference in the long run. However, as you say, AIB have a larger pool of mortgage owners and the government will surely not allow them to increase rates ahead of the rest.
I just wonder if at some stage Ulster Bank will try to build up a bigger mortgage business in Ireland again (based on more sensible lending of course!!). If they do, the quickest way of building a loan book would be to offer lower SVR mortgages.
Yes, AIB confirmed the rate would be 4% (or 4.04% - not sure which one they said) from 13th November. The rate at the moment based on my LTV is 3.54% but that is being increased in November.