Thinking About: The 3x Successor for older D&D is E8

Yes Epic 8, the 3x variant in which the leveling stops at 8 and instead of new levels, all advancement after is in the form of feats at every 5000XP.

My reasoning?

Well E8 (especially with an option to get a level 5 slot with a feat) stops at roughly the hit point and power level of older versions.

With a bit of work it gives you the same relationship to the world that high level guys in AD&D and OD&D had.