Thank You!
I'll allow that you and I, and everyone at CFC may not be entirely objective on the issue.
Ha ha..!! Seriously, Civ V will be better off without CIV IV only if it out ranges civ iv in every aspect and feature of the game, almost as it has happen before with each and every one of civ releases. I've known civ from it's first version and I can asses that this was always the formula for it's transcendence. The final civ iv version, BTS with last patches and even if you want to mix it with some good mods, has achieved a degree of depth, variety and complexity difficult to overcome by some drastically arranged version. Of course there were more than two things to upgrade in civ iv, some of which I read about will come to be in 5 (barbarian system remodeled, city states, and many others). The fact is that if there is at least one somehow mayor feature ripped off the game other than improved civ iv will eternally have it's stand against it's successor.
For instance, No tech trading would be awesome really if there is some contemplated new system which makes technology diffusion more natural and less prone to abuse. If it's just taken off the game will be diminished. Same with religión, it was a great feature, deeply integrated within the entire game at it's proper scope. Removing it or making it more shallow just demotes the depth and historic quality of the game.
I don't know folks, always trusted Sid Meier mainly because what I stated above, every release was undoubtedly better than the previous. I'm just not sure this will be the case again.