The thing is we can't move too far forward because some parts of the world aren't even off the starting line yet! Noxus is prepping for war by the sounds of things, Bilgewater's in turmoil, the Shadow Isles are ramping up, Shurima's entering a new age, Freljord's in the middle of civil war, so what are places like Piltover, Zaun, Demacia, Bandle and Ionia doing? What's up with Targon? Anything void relating on the horizon?
I feel like Riot will be going forward with the intention to actually define all the places in Valoran and its islands beyond names and a few champions. This means things will likely stagnate in specific areas until everywhere's covered and established, all the rules are set and they can progress without worry about leaving some part of the world hanging. As it stands the regions I listed first can have stuff occur in the background that isn't to major and be revisited every now and again, but everywhere else still needs re-establishing so we actually know what the hell's up with them in the new canon.
Of course they could rebuild the world at the same time they advance other stories. They can put out short stories, comics, whatever they feel like and it'll be like adding ornaments and furniture to the rooms in the house, while they also work on constructing the second floor, garden, conservatory and roof. Riot has departments and teams and stuff so I imagine Narrative can actually pull this off to a degree of success.
So suffice to say, they can move the lore forward and continue rebuilding, it's a question of whether narrative want to take this direction or not. Keep in mind Bilgewater not only re-established Bilgewater but it pushed the plot of that part of the world forward., so these things can be done in tandem.
