Nintendo's official translation of their 2020 Shareholder's meeting. They say 'we want to extend the life cycle of the Nintendo Switch' after being asked about their plans for their next system. Their response to question 7, specifically.
Quoting for reference:
That meeting took place June 2020, which was 3 years and 2 months after launch of Switch (March 2017). Extending from that point could simply mean not cutting it short like they did with Wii U, or it could mean not cutting their focus from Switch software short in favor of the next device like they did with Wii. I do think Nintendo will support Switch up to and even beyond its successor coming out, which would be extending its support well beyond what they normally do. Normally when a device comes out, almost everything dries up 1st party-wise for the former device, but I think they will continue to make games for Switch 1 for a year or two after Switch 2 comes out (that also come out on Switch 2). So yeah, I fully expect Switch to have support extended beyond 2023 (which would be their normal end up, if not sooner in 2022), but I also expect Switch 2 to be out in 2023 and also have that software in addition to exclusives that are too taxing to run on Switch 1.