Personally, I still feel that delving should be a separate end game from mapping altogether. Balance it so that delve rewards are equivalent to map rewards at the same difficulty. Then allow players to delve endlessly if they want, or map endlessly, or switch back and forth when they get bored of one.

I can't see myself delving in later leagues if I have to map to get sulphite in order to delve. I already have to fill out a fresh atlas every league, and for me it would just be too much work to do that plus put the effort into delving down to level 270+ every league (the equivalent of T16 maps). And that is on top of whatever new league mechanic will be added in the next league.

Not to mention that GGG has said Incursion will be added in some form next patch. I don't want to have to do maps on top of temple runs and delves, plus a new league mechanic. Let us pick one end game and run it as much as we want. I don't see the problem as long as they are all balanced.