curl, you have been so wrong for so long that you aren't in a position to tell others what to do, except advise them to be not like you. It's not too early to make the call now, the PS5 won't sell more than Switch. Just like it wasn't too early in 2017 to make the call that Switch will sell more than the PS4. The "it's too early" line in a general sense usually comes from people who don't like how things look at the moment, so they want to buy some time in hopes that the state of things gets closer to what they want them to be.
The reasons why Switch was going to sell more than the PS4 could already be known in 2017. The biggest reason of them was and is that Nintendo holds a monopoly in the portable console market, so merely keeping that market flat from generation 8 (~90m between 3DS and Vita) was going to get Switch close to 100m units sold. From there it doesn't need a big vote of confidence that Nintendo can achieve a big enough presence in the home console market to get the necessary sales to beat the PS4 lifetime sales. After all, the Wii U did not represent the ceiling for Nintendo home console sales, it was a complete and utter failure with Nintendo making all the wrong decisions for what they wanted to go for with that console.
Likewise, we already know a lot about the PS5 in late 2020. It's a straight-forward follow-up to the PS4, so the chances that the PS5 will appeal to a broader audience than the PS4 are very slim. One opportunity for growth is to take consumers away from Xbox which appeals to the very same group of gamers, but what we know about Xbox Series X is that this gen multiplats aren't going to be notably inferior in terms of framerate and resolution, plus Microsoft has been expanding their first party studios; this makes it tough for Sony to convince Xbox One owners to go for the PS brand, because Microsoft ticked the most important boxes to retain what they had.
Growth for the PS brand is mandatory to challenge Switch sales because Switch sells better than the PS4, but the realistic options for growth are limited to developing markets growing bigger over time, because the PS5 itself doesn't have the appeal to grow in the matured markets. Chances are good that PS sales decline slightly in both Japan and North America, so the gains the PS5 makes in developing markets will be mostly offset by these decreases.
I can understand why a lot of people have trouble to make good predictions for Nintendo consoles, because Nintendo consoles can greatly differ in strategy from one generation to the next one, but Sony and Microsoft make it pretty easy. The PS5 isn't a mysterious entity where it's hard to say what it is and what it will be, so the general consensus for its lifetime sales is bound to be in the correct ballpark, unlike for Switch where the consensus was off by miles.
I agree on PS5, that it doesn't show any signs on how the market should be grown, so chances are with tougher competition from XBox, PC and streaming services that PS5 will decline or at best stay similar in sales to PS4. I agree that PS5 might lose in matured markets, especially Japan they seem to lose any grip on. I agree that developing markets may grow overall, so that PS5 might sell more there. But the big new markets to open up that helped PS grow in the era of PS1 and PS2 are mostly covered by now, so the developing markets also have limited growth capabilities.
But to be fair it was a lot harder to gauge Switch success pre launch. First it was a new concept with the hybrid, and while many - myself included - was entranced by the concept, I lerned to mistrust such anecdotal evidence. How much the market as a whole would like the concept was not so easy to gauge without proper market research. Another variable is Nintendo itself. They have proved time and time again, that they can be their own worst enemy. Decisions like stopping support of the Wii too early, and then follow up with a direction in the complete opposite of the Wii success make it hard to trust Nintendo to do always the right thing.
One thing you could know about Switch was, that Nintendo probably wouldn't fumble support in the launch year. They had a lineup for 2017, that covered a lot of bases. New sequels in established success series (Breath of the Wild, Mario Odyssey), sequel of their hit new IP (Splatoon 2), new IP trying out some stuff like Splatoon did (Arms), port of a proven successful game (Mario Kart 8) and a game showing off the new features of the hardware in the vein of Wii Sports, Nintendoland and Astros Playroom (1-2-Switch). That are six games for the launch year covering different bases. Nintendo didn't needed all to succeed, but this made clear that Switch probably wouldn't end up being a flop like WiiU.
Still, how much BOTW drove early momentum and how well received the hardware would be was hard to get a grip beforehand. Even for Nintendo themself. Soft launch in March allows for course correction before the first holiday, like they did with 3DS. That launch date shows a bit of a lack of confidence.
So yeah, I agree that something big and unexpected must happen for PS5 to significantly outsell PS4. But the success of Switch was much more of a gamble, because Nintendo didn't just do more of the thing before (which would've been a bad idea anyway, as before was WiiU) like Sony does.