I'd say it's fairly permanent ... as far as I know recently they were operating it only a few days a week (so fairly useless for business travel) whereas SAS are flying twice daily at least ... so SAS would have taken most of the higher fare business traffic with the better schedule and also lot of traffic connecting on to SAS flights to elsewhere in Scandinavia/Eastern Europe & Asia would naturally fly SAS to Copenhagen.
Especially now Ryanair are flying to Malmo which is really just over the (incredible) bridge/tunnel from Copenhagen I'd say it's unlikely that Aer Lingus will be back on the route that quickly ... though you never know !