And that would justify a 50 billion dollar valuation? They would need to create multi-billion dollar market to make it worthwhile. And also learn selling to businesses.

Oh the valuation doesn't mean anything except to new potential investors. It's essentially a made up number that means nothings especially since they are not earning a profit and don't look to any time soon.

But that aside, yes a pivot would require them to do things differently, just as in your example learn selling to businesses However every taxi company in the world would jump at this opportunity immediately. The same industry that refused change for decades and had their parade rained on when Uber came around would greet this change with open arms. Especially if Uber were to 'go away' as a result.

There are going to be down rounds for Uber in the future no matter what, valuation means nothing if your business won't survive.