I'm in waiting mode. I'm assuming it will distinguish itself from #5 right around the 2nd major expansion pack.
Reading some reviews, seems like it distinguishes itself right off the bat. Some I read compared it to launching with 2 xpacs.
That's because it's launching with the features added in the last 2 expansions in Civ 5
Think of the culture changes. Those are stock in 6. It really looks like 5 with a reskin from a gameplay standpoint.
I'd love to be wrong tho.
Having a what amounts to a culture tech tree" is an addition, and the government tree is basically a slightly expanded ... can't recall what it was called in 5. That pane with like 12 options where you chose what type of civilizaton you were. Outside of that, you can stack units again. *shrug* I really can't find any more distinctions.
I'm predict (and hope for) greatly expanded espionage mechanics in the first expansion.