@Riot: What's the plan when class-based reworks are done?

Tanks Divers Maybe Melee ADCS Maybe traditional supports and possibly revisiting early reworks such as juggernauts/ADCs/mages.

With tanks in mid-season (Just a few months away), what will be the plan once all classes are brought up-to-date with Modern League? What's the strategy after that, considering we're getting closer-and-closer to an entirely "modernized" league?

Will we see mid-season items added? Preseasons dedicated to hodgepodge reworks? Completely changing runes/masteries?

I know it's a lot to ask for such a glimpse into the future but what's the long-term plan once we finish class-sized updates?