Based on my business travels mostly related to sales, I don't see any of them shifting online. When it comes to decision making, physical presence matters a lot. This is not some routine weekly status call we are talking about. Courting customers, making them feel good and closing that deal - none of these will ever happen online, unless some magical VR tech comes about.
This is the thing I worry about -- my business requires a decent amount of air travel, and in general business travel is where you hear most of people bopping in and out of town in a single day, whereas vacationing is often for at least a few days.
No question that physical presence is huge, but that doesn't justify it from an environmental POV at all, esp. since most sales are about making owners/investors richer, not making the world a better place.
I think real creative thought about how business travel could reduce impact would be massively impactful. It would probably need regulation, because the sales team that tries to, say, do all meetings virtual will be whomped by the other team that shows up.
