It seems absolutely extraordinary to me that 'the industry' (mainly the airlines themselves and aircraft leasing companies) seem to have tucked their heads back under their duvets and tried to carry on as usual despite now flying through at least SOME ash.
As Sunfish points out, the worst-case scenario is a catastrophic increase in engine maintenance, far beyond the capacity of engineering and parts-supply. Well before that point is reached, there are unpleasant operating cost implications for any operator covering routes anywhere in N Europe.
It would be nice to think that company managements are already fully-engaged with this and are collecting detailed data (from whatever sources) about what quantities of ash their aircraft are being exposed to, on individual flights and cumulatively. However, I've seen or heard nothing to suggest that much is being done.......