Pretty sure what will kill the web isn't proprietary software and non-open protocols.
Nope, what will kill the web is machine-generated nonsense.
Much like cable TV is an unwatchable mess machine-generated content-at-scale will make folks stop using the web.
If companies are smart they'll realize this. But greed is a powerful drug. And unless companies realize that this drug will eventually kill them they will continue to get that high each and every time.