I'm pretty sure this will be the peak year. Nintendo is going to have a hard time matching it's releases this year, especially Pokemon. I also think we'll see a $249 Switch, even if only for BF week.
Unless Nintendo drops to $199 sometime next year, this will probably be its peak year. Not that sales will collapse. 2020 should be relatively close to this year. 2021 is when the real declines will happen.