As I recall Mario's return to 2D in the Wii era led to a revival of 2D platformers like DKC and Rayman. Could 3D Mario's big return have a similar effect?

If you looked around you, you should know that's already happening.

I think we have seen a slight 3D platformer resurgance with games like Yooka-Laylee & A Hat in Time but hopefully Odyssey being a major success can lead to more games in the genre.

Ya, on top of which, it isn't genre that disappeared. 2D platforming did, but 3D has always been around, from your amazing Mario, Sly, Crash, to the smaller indie titles that are popping up.  

I do agree that Crash/Mario will most likely take it to new heights....hopefully we get real crash game after this as well. 

When were platformers gone? Both 2D and 3D have been doing just fine. 3D on consoles and 2D on PC.

No, because other developers are just too incompetent and lack the talent to create platformers even remotely close to the quality of Mario.

I think the only franchise close to 3D mario (in terms of quality and talent) is ratchet and clank, so enjoy ratchet and clank.

I think, in a way, Mario led a resurgence in platforming, just not with Odyssey. It could be argued that New Super Mario Bros. and Super Mario Galaxy have helped jump start it. It just took some time for others to follow suit. Since then, there was Kirby's Return to Dreamland and other Kirby games, DKC Returns and Tropical Freeze, Shovel Knight, Shantae and the Pirate's Curse and 1/2 Genie Hero, Yoshi's Woolly World, Yooka Laylee, etc.

Hopefully not. I've jumped over enough stuff to last a lifetime.