Nah, I think you're underestimating the pokémon fanbase and how gaming fanbases as a whole will mark down how "hype" the marketing has been up until the next installment of a franchise and often compare or contrast it with other games and their waiting periods.
Yes, it's not gonna critically harm SwSh's sales, but the fans absolutely will remember **** like this because half of the experience is waiting to see what gets revealed next and if it can instill hype in you.
The whole reason these boards are active is because we're still technically in a speculation cycle with DLC in the picture and I definitely remember this place being much livelier before Ultimate released because that's how the internet works with gaming media; it's mostly just the hype and then when the game releases, it's the entertainment value that'll eventually fade after a few days, maybe weeks of the intial crowd basically giving their opinions and observations.
Tl;dr: This "hype cycle" for SwSh is pretty abysmal compared to previous games for quite the amount of people. Hell, Dexit is STILL going strong.
Of course they're gonna remember it, but ya'll acting like every single person who saw the livestream is gonna be raging hard, when I'm saying that the rage won't even stick around for long. Let's not underestimate how easily distracted gamers are, dangle a shiny new trailer in front of them, and they'll forget everything immediately. Why do you think Dexit is dying? People were pissed when it first came out, and now people are just apathetic about it, many of which are still buying the game regardless because they were able to look past it, while some just won't buy it.
This is more like the November direct. Remember, people were having meltdowns hard after the long, drawn out spirits segment, and the deconfirmation of many fan faves, alongside Plant. It was a massive hype killer for many, but you barely hear anyone talk about it shortly after because they all moved on past it. It's still memorable, but it's not gonna be something to rage about when times come.
The fanbase will be fine.