I appreciate the OP for making a very thoughtful post.
I've already made a prediction thread about this, but the Switch is going to be the dominant console this time around. In fact, it will be so dominant that it will be the best selling console of all time. Switch is already going to take the entire handheld market, and it will get a portion of the home market too. I believe it will get a majority portion of the home market.
So, the biggest mistake Sony, Microsoft, and Google can make is assuming Sony is the main threat. Nintendo is the main threat this time around, just like they were the biggest threat with the Wii. Most likely the other companies will underestimate Nintendo again, which means they will all get blindsided again.