Decades timeframes get hard, even if we don't take general world events into account; sure the US and western/northern Europe will probably still be fairly rich with disposable income and nostalgia, however if Eastern Europe, middle East, Africa, Korea and parts of south America join the party, all of which are possible and all of which are making good games as we speak today/have done for several years now, then watch that supply-demand thing become even more than it is today when it is mostly still a few nerds that wanted games they had, their siblings had, their cousins had, their friends had, they have played on emulators since and that were in magazines (say a 10 to 1 ratio of desire to supply there).
I will note GC games got expensive about 10 minutes after people got bored of Wii sports and realised it was backwards compatible. I had a GC and built up a fairly nice collection as nobody wanted second hand GC titles when it was current, only wish I had done more as there was a really nice shop where I was at with a surprisingly good range. After that point it got a bit crazy so I went on to xbox or something.
For the Wii U then I will also note a fair bit got remade on later devices in damn near flawless fashion, and will probably continue to do so because high level languages. As it stands we are arguably still waiting on a proper version of Zelda 64 that is not flawed emulators setups or handheld lameness (not sure why 3ds zeldas are so meh when stuff like Final Fantasy 1 through 6 did wonderfully on the GBA) and it will probably be the decompilations that give it to us first much like they delivered Mario 64.
It is very much a never say never thing, and certainly will have Nintendo as a factor, but I would probably put the Wii U more in the Virtual Boy, DSi and such realm where people buy it more for the meme (seen virtual boy prices these days? Not ridiculous compared to many other things but had you stuffed on in the attic for all these years then that will fund a bit of fun) than being quality games*. Most games here were not exactly iconic or truly noted within the franchise (are we going to see debates about the quality of the Wii U mario like we are still seeing about Mario Sunshine in the equivalent amount of years, can you even name the Wii U mario effort without looking it up?)
*I still maintain the N64 was a flop and that N64 games have aged horribly if held to hardware standards (no desire to play N64 perfect dark, will play the XBLA version right now, ditto those on the Rare Replay collection thing, no reason not to play decompiled Mario 64 builds over anything else at this point for me) but they were at least notable in gameplay design and history thereof. Wii U stuff... I guess the Mario Kart speedrunning scene had something going on but I would say Mario Kart lost a lot of relevance with the Wii version and was probably double dash where it last truly left a mark, not to mention Switch version is basically this in flawless/improved form. Give or take Nintendo strongarming competition then doubt will be seeing them take up Wii U Smash Brothers too terribly soon or in the same way the GC version and Wii versions are still held up.
Or short version. "N64 was my childhood console" is a troll signal for us but ultimately nothing too strange and you probably played some decent stuff, might be missing out on some playstation goodness (not that I am complaining too hard as PS1 prices don't need to be raised by Nintendo fan nostalgia as well) but ultimately going to be reasonably versed in things. Wii U was my childhood console (and it has been long enough now that we could be seeing that) and it is probably more a sense of pity that will arise. With that in mind then as much as games are ever useful investments I would not be dropping £500 today on consumer level/sealed but not collector Wii U stuff when I could be doing many other things with the same money in games and probably get far more, far more reliably/safely.
like a 250 dollar kit back when DDR4 was Intel only