Getting 7.7 million in 12 month compared to PS4 is huge.
In 3 month PS4 will be at roughly 63.8 million units. This then is August 2017 for PS4.
In the last 3 month of 2019 Switch sold roughly 11 million.
Assuming 2020 holiday will be similar, Switch then will lead with 77 million -vs- 63.8 million - thats roughly +13.2 million.
PS4 was at 77 million mid March 2018. This will be mid July 2021 for Switch.