Quite a bit unknown about the LE side at this time. However, I would not expect the current system to just disappear. Some of those involved are not that stupid. Even now there are a couple layers of backups in place for countywide communications.
I can say the Fire repeaters will not be going away anytime soon. In addition to the paging requirement, even when the switch is made there will still be a considerable amount of traffic on analog. Most departments are not able to budget for the entire department to have WISCOM radios.
Not to mention those of us that respond for mutual aid or cover a portion of the County. I personally very much like the idea of the regional tactical talkgroups. It's a move towards the "channel pool" concept, but it's not quite there. Until responses are made more regional, both in communications and operations, we're still going to have the normal problems. Other than patching, and only some radios having WISCOM, we'll have to continue using analog for Douglas.
Edit: No known timeline for the switch.