Excited for this as I am just about all Metroidvanias. It's just a very elegant and inspiring progression system for adventure games. Not all of them will be Hollow Knight or Super Metroid, but even the short ones or the clunky ones are still fun. I even like mini-Metroidvanias like the ones created in Super Mario Maker.
I'm still waiting for a 2D MarioVania and a 2D side-scrolling Zeldavania. I don't think we'll ever get one, but it sure is fun to think about. Mario having to acquire a mushroom to be able to break blocks, or to be able to wall jump, or to have a fire flower, or a cape. These abilities would be permanent and stacked. One expansive world filled with inter connecting pipes. Ice worlds and water worlds that you can't enter until you have the right suit. Just call it Mario. Collecting coins would allow you to buy health upgrades or speed upgrades. Yes, it wouldn't be a Mario game...but boy it sure would be fun...and even a little serious.