Maybe, maybe not. Mostly just depends on how busy it is. Since 7 is prime dinner time, my guess is the restaurant will be full and busy. You could try going at 7, but it's totally up to chance as to whether you will get seated before 8 or not.
My last trip, it was a low crowd time. We ended up at almost all our ADR's somewhat early and were seated early most of the time.
One night we had a 9:15 ADR at Narcoossee's and arrived at 8:30. We weren't seated until 9:45!
So if you want to risk having to sit around for an hour, then you could try.