We know that Q1 saw the PS5 at #1 for dollars but the Switch #1 for units, and that the PS5 is LTD ahead of the PS4. We know the PS5 sold 1958k last year, while the PS4 sold 2914k in its first five months, so that gives us at least 956k for the PS5 in Q1 (meaning the estimates we have are pretty close, maybe very slight undertracking). So, assuming an ARP of $480, that's at least $458.9M in revenue for the PS5. There were right at about 1M Switches sold total between January & February, so that gives us a total about $265M, leaving us with at most about $194M for March. That gives us an upper limit of ~730k. Since the Switch was #1 in both units and revenue in March, that gives us a lower limit of ~705k, assuming 390k for the PS5.
So, our likely range for the Switch for March is 705-730k, again assuming that the PS5 disc-to-digital ratio is roughly correct. That's a substantial drop from March 2020, but only a slight decline from February in terms of weekly averages, and still very strong, with the month aided by the $1400 stimulus checks. That would give us a Q1 total of at least 1700k, at least 100k ahead of Q1 2020, where the Switch sold a bit over 1.6M (did we ever get an exact number for March, or do we still have nothing better than that flat 1M estimate?). All of Q1's improvements for the Switch came from January & February, as those were the pre-AC, pre-pandemic months and Switch sales, while, good, were nowhere close to where they've been in the past year.
Looking further into the year and what the Switch's 2021 is up against, the Switch sold 808k last April, an average of 202k/week, essentially flat from March 2020. March got a bump from AC and the initial surge in demand for consoles, while April saw the first round of stimulus checks. March of this year had stimulus checks (and Monster Hunter, but that's never been a system-seller in the U.S.), but April has nothing. Even if the Switch was closer to 700k for March 2021, then assuming its weekly average holds it will still only pull in around 560k for this April. And that's a big if, considering the April 2020 stimulus had by far the biggest one-month impact in that first month. More likely, April's sales will be in the 400-500k range, which would put 2021 in the hole against 2020 by probably around 200-300k. May will likely be comparable to April, which won't help 2021's probable YTD deficit, which could grow by as much as another 100k. The entire May-October period will likely need to be at least 10% better than it was last year for the Switch's 2021 to at least match its 2020 by time it gets to the holiday season. June & July will be where the Switch's 2021 can potentially regain some lost ground, as sales slowed down in those months due to stock issues (365k in June, 340k in July). However, the August-October period was huge thanks to improved stocks. It sold 1.91M in that 3-month span last, an average of ~637k/month, and against that level of sales the Switch's 2021 could once again lose ground to 2020. If the Switch's 2021 is running a YTD deficit against 2020 by the end of October, then it's going to need to have an outstanding holiday season, significantly better than the previous two.
Unless there's some big surprise, there aren't any huge original games officially slated for later this year as of yet. There's the Pokemon Gen 4 remake and Skyward Sword HD, but Pokemon remakes have never been notable system-sellers, nor have Zelda remasters. BotW2 might help, if it comes out this year. Perhaps the best chance 2021 has of beating 2020 is the Switch Pro. However, we have no official announcement, meaning no release date or price is known. Also, not every hardware revision has the same impact on sales. In the U.S., we saw revisions like the GBA SP, DS Lite, 360 S, and PS3 Slim give a significant long-term boosts to sales. Others, like the DSi, 2DS, and New 3DS, had far less impact, causing sales to spike initially before quickly returning to the previous baseline. And on rare occasions, like with the PS4 Pro and PSP-3000, hardware revisions don't seem to have done anything to boost sales. I could see the Switch Pro possibly helping offset whatever YTD deficit the Switch has this year prior to the Pro's release. Whether it does or not could depend on what exactly it is and how much it costs (presumably, it'll be a full spec upgrade, which means it might cost more than the OG Switch.
It's still too early to call, but 2021 being the Switch's peak year is far from certain. We'll have to see how it continues to sell throughout the spring and into the summer, especially seeing as things may return back to normal as vaccinations continue apace and the country gets back to 100% reopened (I personally can't wait for summer blockbusters), which could negatively impact demand for consoles.
I agree that 2021 being the peak year is far from certain but that fact that we are even debating this is crazy as most people last year were stating with confidence that 2020 wont be matched and in fact 2021 would see a significant drop.