They may not "spec" for it in their support documentation, but they would essentially eliminate Nvidia Shield as a competitor for those of us that are hard core home theater peeps.
Still wouldn't replace my Shield if for no other reason than lossless audio bitstreaming. The Shield gives me trueHD/Atmos and DTS:X. Roku won't bitstream anything higher than standard Dolby Digital and DTS.
I think you hit a key reason right there why expecting a Shield killer from Roku does not make sense. No matter what Roku does, they aren't going to get something that hits all the hard core home theater features of the Nvidia Shield and also hit a $200 price point. The Nvidia Jetson platform that seems to be the basis of the Shield hardware has very few true competitors and the ones that do exist tend to be more expensive. An example of the type of price you can expect to end up at as a third-party licensing the Jetson platform is the Nintendo Switch. It is also based around the Jetson platform but costs $300. The Switch also doesn't even attempt to compete as a media player.
So who would be willing to pay more than a Nvidia Shield for an alternative to it? The OP points out to the feature of being able to stream uncompressed UHDs like Avengers Infinity War. But Disney uses BD+ protection on that disc to try to discourage doing that. Hence, it may not be a good look to content creators if Roku used that as a selling point.
Selling that feature to streaming services also is currently of limited value. Several ISPs don't offer speeds above 100Mbps to allow Netflix to deliver uncompressed UHD quality. I also don't think Netflix is even interested in delivering that quality level. Samsung just announced last spring they will discontinue manufacturing new BluRay and UHD BluRay players. Previous to that, the premium brand of OPPO had announced they would be ending their line of players. Right now 125Mbps streaming quality is not a key issue for Netflix to be able to compete with. They seem focused on retaining customers while Disney Plus and HBO Max enter into the streaming market. Those new entries also don't seem to be looking to use 125Mbps steaming quality as a selling point either.
So who is these features for? How many people make up that group? How much are they willing to pay?
Realistically, I don't see how this will really provide a sizable increase in Roku market share no matter how much I would also like to see a premium Roku.
It also supports any caption track contained within my media, while Roku only supports external SRT files. It won't display any captions based on images (which is what all DVD and Blu Ray discs use).
I think you mean the Roku Media Player Channel only supports external SRT files. Roku OS has additional capabilities but even if those were exposed, this is one area that Roku could do well to give some more love to for future versions.
The in-stream captioning support in Roku OS include EIA-608 and SMPTE-TT. As far as I can tell, most video encoders don't support EIA-608 at all or support turning EIA-608 into an SRT, not an SRT back into an EIA-608. It is an old standard that goes back to pre-HD broadcast television making use of the video stabilization bar which is a concept that doesn't really apply to HD.
Of SMPTE-TT which is a bloated over-engineered W3C (World Wide Web Consortium) specification, Roku only implements part of it. They even seem to admit they haven't reach what could be considered minimal compliance.The other disappointing thing is close captioning being restricted to the built-in Gotham font. As has already been pointed out on this forum, the built-in font does not even include such characters as Cyrillic. The Gotham font family has those characters but Roku doesn't seem to license that part of the font or provide a way for users to select to install it. If they switched to the Google Noto font then they could skip having to pay licensing fees and hopefully someday provide a way for users to install additional language characters.I'm under the impression better captioning support would make a bigger difference in the short term than getting a 1gbps network link to a home network switch. While we will probably see a Roku with a 1gbps network interface sometime in the next couple years given how quickly they are coming down in price, but as mike.s has already pointed out there are other hardware
constraints to bitrate playback than just the speed of the NIC.