Xenoblade 2 took about 3.5 years to make

[Nuvendil]

curl-6 said:

Nuvendil said:

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.

It is a tricky thing to spot.  But looking at the overall package, I would say there does seem to be some notable modifications.  Some of it seems to be general efficiency improvements, but other aspects have changed quite substantially it seems.  But it is impossible to know how deep those changes were made in the engine without looking at the engine first hand.