It seems, based on what I've been told, that FASTPASS+ will be rolled out starting to Disney Resort Hotel guests. From there, it really become a guessing game as to when offsite guests will get it. Some have even suggested that it may never happen (though it didn't sound like that in the announcement).
Rumor has it that the first resort to get it will be Disney's Boardwalk Resort. Some say it could begin as early as mid to late February. We'll see...