Is Pokemon GO bringing Pokemon back to those 90`s glory days of selling over 30 million? Will have no impact at all? 

I anticipate no impact. We're too far from Sun & Moon, and Go is already dying out due to Niantic being a terrible developer with zero communication with the community at large. Even without Niantic being horrible, Go would die out once the more hardcore finished collecting and leveling, and the more casual naturally fell off to the next game.

The most glaring difference is that Go is meant to have casual appeal, whereas the main games are a different beast that demands dedication and thought. Casual and dedicated gamers don't tend to have a lot in common in what they're seeking out of their games.

I don't think it will have a big impact in either direction because it's SO basic at the moment.

all of the die hard Pokemon fans (which there are a ton of) are probably a bit annoyed at the simplicity of 'Go'. and I don't think mobile gamers are necessarily going to magically invest in a 3DS. that said a lot of casuals really like Pokemon and already buy the mainline series. Its sort of why a lot of people were not surprised when Pokemon GO was such a hit; when the mainline franchise has EVERY game selling like 10million+ copies then its already extremely popular with casual gamers.

it may get slightly more people interested butttttt the mobile game and the handheld game are like apples and oranges in terms gameplay

https://mynintendonews.com/2016/07/29/italy-pokemon-sun-moon-are-the-most-pre-ordered-pokemon-games-ever/

We are already seeing one in Italy!

I think the games will see a boost. Pokemon Go is pretty simplistic (not to hold it against Pokemon Go considering it's a free app) so it's no replacement for the 3DS games.

There might be a bit of a boost due to people rediscovering Pokemon, and due to some younger gamers coming across Pokemon for the first time thanks to Go. It's definitely not going to boost the series back up to 30 million plus, though.

Pokemon Go was a fad and consumed (percentage wise) mostly by people who don't play the real games. I don't think it'll have much if any impact at all.

You'll be able to use Go to get those pokemon and transfer them to the main series, and maybe as some sort of Pokewalker. the series is going to grow more thanks to the exposure, and that is a good thing.

The previous games already had a pretty big boost thanks to Pokemon Go, obviously it will have a positive effect on Moon and Sun.

Yes.