If you can ship a custom decoder, don’t care about battery life, and have enough CPU headroom, yes, VP9 is an option. For everyone else, until AV1 hardware ships it’d be better to stick with H.264 than use VP9 if you can’t figure out a way to make H.265 work in your business.
VP9 has broader decoder support than H.265. Even when you don't have a hardware decoder, the software decoding for VP9 is not bad. I play VP9 video in VLC on my iPhone 7 and I have survived to tell the tale. It's not all doom and gloom.
Yes, an iPhone CPU is usually fast enough not to drop frames but if you care about battery life it’s not competitive. Again, I’m not saying that VP9 is bad but rather that anyone serious needs to support both formats until AV1 has MPEG-4 levels of pervasiveness, especially if you’re publishing on the web.
No, if you're publishing on the web using VP9 is the better choice. VP9 is supported in more browsers and there's no point having the licensing hassle of H.265. And as Netflix found, VP9 outperforms H.265 by 12% with the right encoder:
