Switch was successful long before Pokemon Let's Go was announced though, that game is simply just carrying momentum the system already established 16 months prior.
And games 4 years from now will likewise simply carry momentum established by the evergreen killer apps of now, next year, and beyond. They can look as outdated then as Let's Go does now and it won't matter.
On the same system? I doubt it. Not unless Nintendo is OK with yearly shipments in the 5 million/year range.
You're turning the Switch into the 3DS if you're just going to let the chipset age that badly, and IMO the sales appeal will drop to a more narrow audience.
By the end of 2019 alone, Nintendo will have burned through the following franchises:
3D Mario, 2D Mario, Smash Bros, Zelda, Mario Kart, Pokemon Lets Go, Pokemon Gen 8, Animal Crossing, Fire Emblem, Splatoon, DKC, possibly Metroid.
That's pretty much most of their A/B-tier roster. That's also a big issue. Yes you can make a Mario Odyssey 2 or Mario Kart 9 even, but you're not going to get large hardware boosts in the same way because large portions of the fan base for that IP will already own a Switch.
A new Switch model with a legitimately higher end chipset that is comparable to what the XBox One X and PS4 Pro (2-3x the power of the base unit) around 2020 are to their predecessors will boost Switch yearly sales, there's just no way it won't. From a business POV it's the right play.
There's not even any loyalty that you get from the "we want 5-6 years of support no matter what!" crowd, did Nintendo get any loyalty for supporting the Wii for 6 years? Nope, that audience base dumped them like a bad habit with Wii U. Supported the DS for 7 years, and lost half their market with 3DS. You get really very little "bonus points" for pleasing a very small portion of the overall consumer base. Yet everyone and their grandma bought a DS after they only supported the GBA for 3 years.
Last edited by Soundwave - on 28 November 2018