Can 7th Gate Guy defeat them?

I'm asking this because Guy said along the lines of "at this rate, I'm gonna open the 8th gate-" and was cut off by Kakashi because Guy would die. Does this means that 7th gate is not enough to defeat them?

I'm asking this because Guy said along the lines of "at this rate, I'm gonna open the 8th gate-" and was cut off by Kakashi because Guy would die. Does this means that 7th gate is not enough to defeat them?