thats not true!
tekken 6 sold in the first 5 month 1,15Million Units
while tekken 7 sold in the first one or two month 1,66Million Units.
no one knows the current number not to speak from the final lifetime numbers in comparison to previous titles.
thats something we have to see in the future.
it already catched up with sfv on pc in term of units sold and there is still content coming which might lead to more sales.