As of now, most multiplatform games are being released only for X1 and PS4 and this is unlikely to change for the rest of the generation, many say that the Wii U is "doomed" because it lacks such essential third party support, unsurprisingly Nintendo is having a hard time meeting their own expected sales for their console. It was obviously a risky move to release first without being certain of the hardware that would eventually become standard for next gen, but it was also necessary because the Wii U had lost its momentum long before. But what could have happened if Nintendo had moved their cards differently?
I think that Nintendo could have made the Wii U successful if they had designed and marketed it as being upgradable and futureproof (I'm not a fan of upgradable consoles, but at this time Nintendo was in a special position because of releasing early). They could have achieved this in two phases: the "first phase" would be focused in making a competitor to the PS3/X360 and a successor to the Wii, this Wii U would have an empty hard drive bay, a replaceable RAM dimm or an empty RAM socket in addition to soldered RAM, which could be as low as 1GB or even 512MB of RAM in trade for a faster processor. This way the system has barely enough RAM to match the system features of the PS3/X360, in the games department it would be able to outperform them both because of the much faster processor and/or graphics processor (while still being limited by RAM).
The "second phase" would come as early as when the X1/PS4 specs were finalized or shortly after their release, the objective of this phase would be matching specs with X1/PS4 to unleash the true potential of the Wii U and guarantee multiplatform compatibility while enabling new system features. For this, Nintendo just had to release a module of RAM and a hard drive as an addon for existing users. From this point, the console would only be manufactured in its "second phase" with a soldered RAM module of 8GB and a built-in hard drive while being marketed in this final phase as a next gen console. They would avoid segmentation of their install base by making the "second phase" the standard version which would encourage early adopters to upgrade.
