Family and kids may be the main buyers and audience NOW... 8 years in, going on Year 9, with the successor around the corner, which is why I don't think Switch 1 is going to fall off drastically once Switch 2 comes out. It is going decline and we will be able to tell, there's no doubt about it. But it's not "cliff theory." Because the audiences and people buying those systems are going to be drastically different...
The people buying Switch 2 at launch and Year 1 are going to be the dedicated gamers and loyal, diehard Nintendo fans like many of us are who bought the Switch 1 at launch or Year 1-2 because they're that committed to the product, actively follow it, and talk about it on forums and websites such as this one.
The people buying Switch 1 in Year 8-9 and onwards are the very casual, average Joe and Janes, parents who just want something for the kids and family members who are new to gaming and want to hold them over. Now when Nintendo reveals more info about Switch 2 and we know its launch price, and how many games are backwards compatible, some of those parents and casual consumers may decide to just hold off and save their money to invest on the platform that they will be supporting in the future. But some, dare I say, the majority, of those consumers, will just jump on Switch 1 now because it's already out, it has so many games already, it's easy to jump into, and it's convenient. And if Nintendo actually gives all the Switch 1 models price cuts, that many more consumers will decide to jump in right away to get themselves started, then when the time is right, will jump to Switch 2 in Years 3-4-5, right when that system is at it's peak.