Xenoblade 2 took about 3.5 years to make

[curl-6]

Nuvendil said:

caffeinade said:

Perhaps.
But in the same way CoD: WWII is built on id Tech 3, or Titanfall 2 is built on Source.
Both games use Heavily modified engines, that only vaguely resemble their parents.

XBC2 is pretty much just built on XBCX's engine.

True.  But worth pointing out, XC2 features a number of improvements and notable changes to the X engine.  It's not just a new game on the same engine.

It's hard to tell; graphical upgrades don't necessarily mean sweeping improvements to the engine itself, it may simply be that stronger hardware allows the same engine to do more than it could on Wii U.