OK, so you're conceding that you don't know the general business model these plug & play machines follow.I doubt you will see that. If anything you will see an SNES Classic or N64 Classic. I'd be shocked if Nintendo's plan is to offer an NES Classic 2 with 30 more games. If that were the case they wouldn't put Mario 1, 2 and 3, along with Zelda 1 and 2 and Metroid on this thing rather than spacing them out. This is a one off thing. I'm not sure how that's not readily apparent. I don't think Nintendo has any interest in creating an ecosystem for this device. The reason this thing got so much mainstream buzz when it first was announced is because it hit the perfect nostalgia spot with the kind of consumer that doesn't care about Amiibos or expansion cartridges. They get 30 classic games to mess around with of varying quality and popularity, get to scratch that nostalgia itch, and get a stocking stuffer for the holidays. It's not any more or less than that.
NES Classic 2 wouldn't have a totally different lineup of games, because that's not what happens. What happens is that the subsequent releases add a few games and subtract a few others, but the core lineup largely remains the same. Hence the question, "are the people that bought the first revision going to buy another largely identical piece of hardware to get a new game or two that was added?"
I get where you're coming from with "most people wouldn't buy anything past the inital purchase," and that's true! As it is with most purchasers of things! It doesn't negate that add-ons can be a significant revenue stream. For every ten people that buy the thing and throw it in the closet, there's one that would buy a handful of expansions if they were offered. It's a little silly to take a hardline stance that the market for something that would pretty obviously appeal to Nintendo diehards is negligible, considering that Nintendo just sucked in over a billion dollars selling little barely-functional tchotchkes to that segment of their market. You're gonna tell me that figures celebrating obscure Nintendo characters could sell by the boatloads to them, but nicely-packaged, officially-published collections of full NES games would be met with total apathy?