No it will never supplant H.265 and it's open but not necessarily free.
The number of companies supporting H.265 far exceeds AV1/VP9 and the biggest wildcard is: Apple. You simply can't have a codec that doesn't work on iOS or OSX. End of story. And you already know who has won by looking at torrent sites which have almost zero AV1/VP9 content but lots of H.265.
And we already know that VP8 was riddled with patent infringements and ended up getting a license from MPEG-LA. VP9 has not yet been tested in this respect and could easily require royalties from implementers in the future.
H.265 does not have a clear path to victory over VP9. Even with only YouTube serving VP9 I suspect it's already much more widely used than H.265. Given the current state of the world it seems more likely that Apple will be forced to support VP9 in Safari than the other browsers being forced to support H.265.
Where have you been ? H.265 is shipping on far more hardware today. It's been shipping on Intel, AMD, Nvidia components for years and is the standard codec for the PS4 and Xbox One. It's also the standard for broadcast terrestrial TV which means set top boxes, TVs etc.
And Apple is a patent contributor to H.265 so zero chance of adopting VP9.
HEVC (H.265) is only used in germany for DVB-T2 (all other countries do use H.264). And DVB-T2 is not in widely use (even DVB-T was a failed product). I guess the only users of DVB-T2 are campers.
(edit: Currently DVB-T2 is only free for open senders (ARD, ZDF, senders which are paid by the "Rundfunkbeitrag", the rest costs money. it's not in wide use and probably never will Astra Sat / Eutelsat or cable (DVB-S2/DVB-C which all only use H.264) is probably the way which most people go, after the DVB-T debacle. And heck even than H.264/H.265 is implemented by DVB-T2 vendors but DVB-T2 does not need H.264/H.265 it can be used with AV1 aswell.)
The number of companies supporting H.265 far exceeds AV1/VP9 and the biggest wildcard is: Apple. You simply can't have a codec that doesn't work on iOS or OSX. End of story. And you already know who has won by looking at torrent sites which have almost zero AV1/VP9 content but lots of H.265.
And we already know that VP8 was riddled with patent infringements and ended up getting a license from MPEG-LA. VP9 has not yet been tested in this respect and could easily require royalties from implementers in the future.