What kind of progression is in the game for every Pokemon?

As a big shiny hunter I’m curious to see how you could hypothetically (I imagine nothing has been confirmed by the people who have played early yet) boost the odds of each Pokemon in the game, are there tasks you do for each Pokemon like in PLA? Is there a reason to use the same species of Pokemon or catch them over and over again? I’d figure it’s more geared to battling this time around but I’m hoping there’s a solid grind to be rewarded for in some way