Eh, I wouldn't actually agree with that.
Personally I don't see any real downside to a CD-based N64 winning Gen 5.
Maybe he means that if Nintendo won then we might not have a "big three" now.
Predictions (Made July 2019)
LTD: PS4 - 130m, Switch - 110m, XBO - 52m 2019 : PS4 - 15m, Switch - 18.8m, XBO - 4.8m 2020: Switch - 22m (Peak Year)