One thing to think about is that EDACS has been reported to have support ended by the current owner, Harris, during 2017. Now the lack of support from the supplier doesn't mean that the systems will all shut down immediately, but the owners of a system that is no longer supported should be actively looking to migrate to one that currently has support. Support of older systems is important when things start failing (and older equipment has a larger chance of failing) since spare parts is more difficult to get. As more owners migrate from their old EDACS systems, their old equipment may be available for owners of systems that are still in operation so spare parts are out there. One serious issue is that your system may have certain features, firmware, accessories, or software that may not match that used equipment and it's up to the owner to figure it out since the manufacturer is no longer there to support you.
Harris has indicated that their P-25 system is what their unsupported system owners should be thinking about. Since this would be a total rip out the old and replace with the new (except for a few things like feed line, antennas, etc.), it's a good time to think about other brands, if that option is available to the user (e.g. the system's owner isn't locked into a sole source agreement or other such issue).