Because of the way job skills are earned, I highly doubt level increases will be as small as increments of 5. They'll need to be +10 or +15 at least, unless they want to cram in more than 1 job quest per 5 levels, which I don't think they do. Also, since the job questlines all ended relatively conclusively, I'd imagine they'd want to write follow-up questlines to be at least 4-5 quests long. Also, the current highest ilvl crafted gear is ilvl 70. Level cap increases would most likely affect crafting/gathering classes as well. Taken together, I predict that the first level cap increase would be to either lv 70 or 75 and there won't be another increase for a long time. This would allow the developers to write robust follow-up job questlines and give crafters access to (current) 2-star recipes while below the new level cap.

I'm of two minds about the effect of a cap increase on ilvl. I think it'd be silly to have ilvls that go further and further above 100 but I also think it's messy to "nerf" the ilvls of existing equipment, even if you don't change the stats at all. Overall, I think I'd prefer the latter though. I don't want to be a lv 75 white mage in full ilvl 250 gear or something ridiculous like that. Just gently rescale the ilvl assignments with each new tier of gear without changing the stats, such that ilvl 90+ is always the current "best".

Level cap increase has been stated to be at the first expansion, don't expect it or new jobs/classes before then. 3.0 expansion will most likely include Ishgard and two of Ala Mhigo, Sharlayan, or Garlemald, whichever makes the most sense. Musketeer is almost a guaranteed lock. Since Limsa is a pirate city, Corsair is a likely job to attach to it. Two or three current classes will get alternate job crystals which may or may not change their role in the "holy trinity". Two or three new classes will have guilds in Ishgard/another new city. Perhaps something holy-related to the religious city of Ishgard? Ninja/Samurai/Thief is currently unrepresented in this game and a likely candidate as well. Feels a bit early for Blue Mage but I could be pleasantly surprised.