December 2020 is the 55th month that the Nintendo Switch has been available for. During the latest month, the gap grew in favor of the Switch by 4.38 million units when compared to the DS during the same timeframe. In the last 12 months, the DS has outsold the Switch by only 152,728 units. The DS is ahead of the Switch by 1.18 million units.
It's highly unlikely that the Switch will ever reach the DS in lifetime sales but the fact that it's outperforming it at the moment is insane.