I don't think there will be another format war again. Blu-ray was the last.
Understand, if 'Blu-ray gets better' - it is actually another format.
4K UHD Blu-ray discs can't play back in standard BD players. Just like BDs can't play back in DVD players, and DVDs can't play back in CD players. 4K UHD Blu-ray is actually a new disc standard. We may see 8K Blu-ray come along some day, and that will also be an upgrade. It may be based upon the current BD standard with 4 or 8 or 10 layer discs. Or it could be something a fair bit different. But, there is not enough market left for another format war like HD-DVD vs. Blu-ray.
The ridiculous jump for people to 4K on their 40" displays they view from 12' away is a joke as it is. Then they watch their 1080i 13Mbs cable television and rave about what an improvement it is. *sigh*
Streaming is the future, but it's a future of convenience rather than quality. It's the MP3 of the CD. Like it or hate it, those that care about video quality are generally going to be screwed in this entire process. Making TVs that are higher and higher quality in terms of video, while delivering video that actually is of lower and lower quality.
A 4K stream at 25Mbs is slower than what Blu-ray has delivered from day one with their 1080p video. So, the benchmark for video quality will remain Blu-ray. It has already moved to a new format with UHD Blu-ray. It may move forward again in future years with 8K Blu-ray. But, it is the last time there will be a major format war.
HVD doesn't seem to be a likely format to move into the market. It is a heck of a technology in terms of storage, but isn't supported by a Sony or a Panasonic. As well, since computers are ditching optical drives completely, the use in a computer is pretty much meaningless. It would find it's market from gaming consoles and movie players, which are showing no rush towards the UHD format, let alone something beyond that.
Remember the real buzz around Blu-ray? There was quite a bit. Certainly the format war sparked some interesting discussions, and it was all over the pages of the magazines.
How about UHD Blu-ray? Not so much.
Eventually, I expect, all the Blu-ray players will become UHD players. It's just going to become the 'standard player' that people buy. If there is a follow up for 8K, it will likely follow the same path. Slow, trudging, no dazzle or excitement. It will most likely fit right into the round hole that Blu-ray has created as a format and will be the last physical media format that any of us will remember.