In order to have DV bitstreamed to the display, the Dolby DV libraries have to be used. It's what Dolby provides to game developers for instance, as well as anyone willing to pay the fees (Dolby has a developer program, see
here or
here).
What is coming to LAV filters according to what I see in the GitHub commits, is the ability to use the DV metadata to perform color space conversion and tone mapping. The display will not switch to DV mode and will not receive DV metadata itself, but instead will be used in HDR10 mode, with LAV video performing the necessary mapping and conversion operations to properly render the HDR content. Also, as far as I can tell, this mapping will not use the display characteristics (DV displays have their calibration data stored inside in order for the DV chip in them to perform conversions and mapping customized to the characteristics of that display), likely because LAV video has no access to that data, but instead will do conversion to standard BT2020 primaries and gamut. Also, same is coming for HDR10+ video streams. I might be wrong about this, but that's what it seems to me by looking at the commits.
Edit: I've just tested this new functionality, and it seems to work fine for Dolby Vision 8.1 Profile files, but it does not work for Dolby Vision 5 Profile files. The test files used are official Dolby DV mp4 files from this
page. Both files work fine in Microsoft's Movies & TV application with the Dolby Vision extension from the Microsoft Store installed.