Audio is unlikely to change from the Switch where it's just pure LPCM.I know the boring answer is we won't fully know until it's revealed, but until then what specs would you expect to be required for a TV and audio system that accommodates Nintendo's next gen device? I want to upgrade but don't know what to look for.
For video, 4k is likely to be the top resolution, but individual features are murky. HDR seems fairly likely. VRR is reasonably likely but not guaranteed. 120Hz is plausible, but probably pushing it a bit. If you get a TV that supports all of those, you're unlikely to miss out on anything, but may be over prepared.
Like you said, though, the real answer is to wait until more details are announced.