The closest there will be to a "reboot" will be a Flashpoint, or Crisis on Infinite Earths type type "reboot", which would likely keep the same cast, and likely wouldn't reboot much of anything.
It would probably just be more of an event thing, and not to reset anything really.
If they do it that way, which seems likely, it could be a missed opportunity, as universe wide reboots are kind of DCs thing, and are the perfect device to allow them to replace actors, et al, when people are wanting out of their roles perhaps.
They certainly laid the ground work for it, especially with the expanded universe, as opposed to cinematic universe, allowing them to really play with the different universes.
As much as many wanted conjoined cinematic and tv universes, I think the multiverse approach is smart, in multiple ways.