My prophetic guesses would be:
1. Within a week or so the following systems will be completely usable: Gold Saucer, 3D-Radar (including PotD and HoH), Scenarios
2. Also on that initial fix-release crafting and gathering will be sporadically working (this means, old actions will most likely be usable if SE doesn’t change too much, but new crafting and gathering actions + new recipes and nodes will only partially work, if at all
3. Crafting and gathering will be completely done within the first month or so. Combat as well, up to the level, Miqo has already finished, if not too many combat actions have changed
4. New systems and new combat stuff will be done within a few months (maybe 3-4 months)
However this is all speculation, based on how it worked last time when Stormblood launched.