Yeah. You'd have to be on I-65 coming down south to get affected by it, but it shouldn't screw anyone else. It stinks to lose the exit to West St., because that goes right by the ICC. It's such an easy route. But, well, that's construction season.
I guess folks coming down from North/North-West could just stay on I-65, overshoot, get on I-70, and then exit west at Ohio. That's probably the least stressful detour. Ohio would cross all the streets a Gen Con person would be familiar with - West, Meridian, Illinois, etc. - albeit it'd cross north of the Circle, which is quite a bit north of the convention center. It's doable. They'd just have to make sure they don't try to turn south on a one-way street going north. ;) :D
If people were masochistic, I guess they could orbit around the west side on I-465, but man, that's a long way to go. Too long, in my opinion, but it might be less confusing for an out-of-towner.
But there's no panic to be had here; there are ways in. This is an inconvenience for sure, but it's nothing more than that. And it won't even be that if the road crews meet their deadline.
Late edit: If anyone traveling from outside Indianapolis reads this, I screwed up. You don't get on I-70 itself. I just looked at Google streetview to verify. When you're on I-65 heading south, there's already an exit for Michigan, Ohio, and Fletcher.
It runs alongside I-70, but it's sort of it's own route. Just keep on following that exit until you get to the Ohio St. offramp.
Of course, there are other ways in; I'm just correcting the one I suggested.
Yeah, that mistake above is all mine. I don't live in Indy, I just have occasional business trips there.