My take I don't think there was ever an expectation that Schumer was going to introduce a bill that federally legalized weed, Decriminalization is the same as legalizion , Think about it , It's a play on words. It's going to be a heavily regulated sector but it won't be federally illiegal which is the main issue preventing growth and expansion in the US.
Dont forget that Republicans have also filed separate bills for cannabis so that shows that there is bipartisan support on both sides of the aisle. I believe that there is enough meat on the bones between the currently filed legislation to push it across the finish line. Over 60% of Americans support cannabis reform so you cannot ignore that fact , it would be political suicide in my view. As far as Biden's support goes , Schumer has gone to bat and worked extremely hard to support Joe's agenda so at the end of the day I suspect Joe will support legislation at the end of the day.