Well here's the thing, BOTH Hardy's couldn't stay sober enough to really make greatness of their careers. Now they're both slumming it out on TNA while Edge retires after retaining the title at Wrestlemania. So I guess the better question is what the Hardy's will be remembered for because NEITHER of them got to Edge's level.
And to your point, I don't think that they were dumb in having Edge beat Del Rio, it is WAY too soon for him to hold that big a strap when all he has as a finisher is the Cross Arm Breaker. I'll admit, his mechanics and fundamentals are amazing, but you NEED FLASH to be a champ. I think that Del Rio WILL hold the strap within the next year, but he needs more time.
As for the WHC, they're probably going to leave it Vacant until Extreme Rules. I could see maybe a 4 man TLC Match with Christian, Del Rio, Cody Rhodes and maybe Drew McIntyre or someone else. But I think they're going to honor Edge by giving his longtime friend and partner Christian his first World Heavyweight Championship.