It is fairly obvious that - long term - the dual EELV system is not sustainable, either Atlas or Delta must go.
IF Falcon Heavy works as advertised, then the rationale to keep Delta alive goes away.
The reaction from ULA and its parent companies should be to try to develop a new system that would be cost effective in comparison with SpaceX, but I don't think that such a move would be possible in their universe. Dissolution would be preferable to cost reductions.