I think the impact of walks and the number of walks will significantly decrease as we move further away from the steroid era. A lot of what is known about baseball from Saber metrics was devised from corrupted data. Walks, bit to be more clear batters who draw pitches will always be important but I think we are going to see a much different brand of baseball in the future.
The impact of getting on base will never diminish. Neither will be hitting for extra base hits. The steroid era saw an explosion in this but getting on base and hitting for extra base hits has always been the best way to score runs and it always will be.