[generalizations]

> how would the world look now

Computer system security would be vastly superior, I imagine. Webpages would be mounted file systems with restricted permissions systems, and browser apps would be command line utilities. Both would have benefited from the same security that UNIX systems use these days.

[pcwalton]

We've had sandboxing for a decade on mainstream operating systems with mainstream browsers. I doubt that just adopting Plan 9 would offer any meaningful security improvements over the status quo. It would just be switching a big pile of non-memory-safe C++ for a big pile of non-memory-safe C.

[pjmlp]

Well, at least we will be using C Machines in a decade, if the trend for hardware memory tagging keeps going on.

[yjftsjthsd-h]

Given that webpages aren't static today, it seems just as likely that in that universe sites would expect you to execute them natively, mounted over 9P. This actually could still work out since Plan 9 did could easily sandbox things, though the security angle would still make me nervous.