I looked at this early and came to essentially the same conclusions as you. I doubt Trump will win by 6%, however. I think enthusiastic Republicans are contributing to the in-person voting and will cannibalize the election day voting. I think the trends are showing a Trump victory slightly larger than Romney’s.
I think it probably does cannibalize a bit of same day voting, but keep in mind the decline in AA turnout we’ve seen so far will also likely occur on election day as well, more than offsetting it. And if trump picks up net 50-100k votes on Ind more than Romney, easily could be near double digits (In 2004 when Obama wasn’t at the top of the ticket, Bush won by 12% here and he wasn’t picking up nearly as many < $75k as Trump will).