In the last year, TI2 showed us during the last match total amount of concurrent viewers including China 570.000.
I havent found anywhere numbers for this TI3, cos they didnt show it in the last match and because I am not patient I am making this tread oviously.
Let me do some calculation.
Twitch tv had 490kviewers
In dota tv were about 150k - 225k viewers.
China had about 150k (it was low, because they didnt have any chinesse team in finals)
= 800k + Swedish, Korean tv and idk what else.
I have no idea what exact numbers are tho. I am just trying to guess it, but it seems like the number will be more than a milion.