What's the general assumption about Civ IV vs Civ V? Which is "better"? Also will we possibly see a sale on Civ V?
I can't speak from experience, but generally, it seems that Civ IV has deeper mechanics, while Civ V has prettier graphics and better accessibility. So in that sense, big Civ fans might say IV is better, while casual strategy fans might say V is better.
Personally, I'm going for both. I'll start with V and graduate to IV.
If you've never played a Civ game or anything like it, you're probably better off starting with Civ5.
If you're a veteren of 4x style games, then Civ4 definitely provides a more complex, deeper, and more advanced style of gameplay. Not to mention there are a ton of very well made mods that make radical changes to gameplay/setting/mechanics/etc. Check out Fall from Heaven, Rhye's and Fall of Civilization, and Realism Invicticus to start. Between the base game and those 3 mods, you'll be busy for months and years to come.