There's theory and there's practical. My suggestion would be to look at what currently exists. Currently, Netflix and Amazon both have a fair amount of HDR 4k content. Both of them support both HDR10 and Dolby Vision. Here are more details in their site for
Netflix and
Amazon. My TV: LG B6 supports both. I can assure you that HDR on 4k is breathtakingly beautiful and well worth buying a 4k HDR TV for. If you wait for the industry to "settle" on the right HDR format, I feel it will be a birbal ki khichdi. It will never happen, and instead someone will come out with a 8k TV and some new format. They have to come up with these new formats constantly to sell more TVs and to keep creating hype. I really feel HDR10 and Dolby Vision are both here to stay and will represent most of HDR content - currently and for a few years to come.
I do not at all think HDR 4k is anything like 3D or curved or what not. It is indeed the real deal - the benefits are real, and there's reasonable amount of content you can currently enjoy. And as for streaming, Netflix requires 25mbps bandwidth for streaming 4k HDR (3mbps for 1080p) which is very much doable, i feel.