With the latest NPD results it seems the Switch isn't reaching the same audience of the Wii and DS. It's like it has a lower baseline, and that is probably because like any core console audience, the Switch audience respond directly to game releases. And we all know the Switch doesn't really get a steady stream of big game releases. The PS4 and Xbox One do, however.

This year so far alone they both have had Monster Hunter, Far Cry 5, God Of War which have driven sales for these systems. It seems Nintendo's first sales driver on that level they'l get this year will be Smash Bros in the fall. And then what if Pokemon is a 2019 game?

Is there a way Nintendo can produce more sales spikes for the system?

Switch is doomed i already predicted it would be at 33 million in may next year

Smash Bros + Pokemon in this FY with some other games like Fire Emblem, will hit 20m mark.
If Pokemon is 2019. game but everything points it's this year game, Nintendo will probably have some other heavy hitter for this FY alongside Smash Bros. Also they can always start making bundles or make price cut if things dont going buy plans.

Switch is selling better than XB1 desipte XB1 had Monster Hunter, Far Cry 5, AC Origins...also Switch sales until now are very comparable with PS4 2nd year on market.

The greatest drug ever: coke Pokemon

Well, yeah. We already know Smash is coming , so is Pokemon. those two alone will drive sales. Nintendo wouldn't project 20 million sold if they didn't have the software

Pokemon, plain and simple. Along with Smash Bros. Those two alone would probably get it really close or well over. Factor in other games like Octopath Traveler, Fire Emblem, Yoshi, and anything announced for E3 and I think it'll actually hit above Nintendo's goals. It just depends on if Nintendo can make enough Switch units.

Things are relatively slowing down for Switch at this point in time but a game like Pokemon will easily cause shortages of Switch units.

Plus:

-Mario Tennis Aces, BlazBlue: Cross Tag Battle, Ys VIII: Lacrimosa of Dana, Crash Bandicoot N. Sane Trilogy, Wolfenstein II: The New Colossus, Captain Toad: Treasure Tracker, Octopath Traveler, Sonic Mania Plus, Splatoon 2 Octo Expansion, Mario + Rabbids Donkey Kong DLC, Xenoblade Chronicles 2 Expansion Pass, Ōkami HD, Monster Hunter Generations Ultimate, Yokai Watch 4, SNK Heroines: Tag Team Frenzy, Ark: Survival Evolved, Dark Souls Remastered, Wargroove, Disgaea 1 Complete, Mega Man 11, Valkyria Chronicles 4, My Hero Academia: One's Justice, Super Smash Brothers,Travis Strikes Again: No More Heroes, The World Ends with You: Final Remix, Fire Emblem 2018, Yoshi 2018, etc

-All E3/Nintendo Direct/1st/3rd Party Unannounced titles for 2018/early 2019

-Advertisements/Marketing

-Limited Edition Consoles/Joy Cons/Controllers/Accessories

-Any and all Switch Black Friday Promotions/Bundles/Holiday Price cuts

It's top secret. Nintendo CEO only knows.

Games, advertising, bundles, holidays, possibly a price cut

Tbh...not much this year. They need a considerable price cut if they want to achieve that. Pokemon is going to do a lot though.