I know this is incredibly unrealistic but I think Nintendo/GameFreak/whoever codes Pokemon Go should put in a few Gen 7 Pokemon around 2 weeks before Sun and Moon and constantly put stuff about it. Would really boost their audience given how popular Pokemon Go is.
I was thinking that too, like they reveal to us the entire evolution families of all the com mons they've show us thus far and put them in Pokemon Go as a promotional push. Then a few months later they add the rest of the Gen VII Pokemon including Starters (why exclude them from the promotional push? So their final evolutions don' t get revealed. Though I suppose they could just disable you from evolving them until Sun & Moon is released).
I was also thinking maybe though could add a Gen VII fighter to Pokken, or at the very least a Support duo (or both!). Obvious choices for a fighter would be Magearna or Tapu Koko (or maybe they could do something with Zygarde and its new forms), however Pokken has surprised us before.
Would Pokemon Go Effect Sun & Moon Sales?
I would say yes, but not by much. If anything it'll maybe convince ex-Pokemon players to come back and try the game. However I think just in general Sun & Moon had already attracted its audience so GF/Pokemon Company just has to convince them (and those who are still teetering on the edge of buying it or not) to stay on with showing us some of the new Pokemon, characters, mechanics, and what the Alola region has to offer.
However I feel Pokemon Go is just too different of an experience from the normal Pokemon games to be any major player in Sun & Moon sales:
Device Platform: Pokemon Go is played on touch phones which most people have now since everybody needs a phone nowadays, but all these people may not have a 3DS.
Casualness: Pokemon Go can be played, well, on the go. Its a very casual game you can play while going places, you don't need to put aside time to play it But you do for a Pokemon main game.
Social: Pokemon Go has you actually physically walking around, exploring the places you are, like a "real" trainer. And it's not just you, you may be doing this with friends or stumble along other people playing Pokemon Go. Share stories and experiences, maybe explore together,
trade,
battle (come on Niantic, I can understand not having long range trading and battling but no local?). However the main Pokemon games are pretty self-contained. Yes there's the PSS and GTS but the level of social interaction there is limited. Also its very likely you're not walking around but sitting down and either paying attention to the story going on in the main game or competing in a battle or any of the additional activity in the game. Also you'd want to be focusing on the game's graphics, Pokemon Go's simplistic display was made that way as you're suppose to use your phone's camera to make it feel the Pokemon is in the real world.
Nostalgia: Pokemon Go is made for the adult players which is why is launched with Gen I Pokemon. Sun & Moon will mainly focus on the new Gen VII Pokemon and have Pokemon from all previous generations, not just Gen I. I would assume the ex-Pokemon players playing Pokemon Go probably stopped playing after Gen II so that's 4 gens of unrecognizable Pokemon they'll be introduced to plus the new ones.
A person who likes Pokemon Go may not like a main series game for these reasons. Needing to buy an exclusive gaming platform, having to learn these battling mechanics, having to it down and focus just on the game while not finding new places or meeting anyone (in real life), and being constantly bombarded with generations of Pokemon they might not recognize (and develop an opinion on). Some people have places to go and people to meet and when they have time off from school or work they want to spend it doing something they like (or sleep).