I simply do not recall ever hearing of a hardware announcement and a launch a couple months later. Seems highly unlikely. Plus doing as such would be horrid for PR. You buy a $300 Switch for xmas to find out a week later there is going to be a better version...... yeah, brilliant marketing strategy. A great way to alienate a whole bunch of consumers.
I mean the Switch itself was officially unveiled in late October 2016 and launched in the first week of March 2017. Which is basically like 4 months. And that was OK because Nintendo had nothing that holiday season anyway (Wii U was dead and 3DS was geriatric by that point). PS5 was officially unveiled in June 2020 and launched 5 months later in November.
It's not the 1990s or 2000s anymore. Popular electronics being unveiled even a week before launch is normal for consumers (see Apple iPhone).
4-5 month lead time is more than enough in the 2020s.
You're going to piss off people who have just bought the older model at some point no matter what that's unavoidable, what difference does it really make if its late January or say April, that person's Switch they got for holiday that previous December is still going to be "new" in their eyes.