More likely they'll separate the OS and the TV code so they can ship the open source OS along with their closed source software
I'd be amazed if this wasn't already the case. We've already been through this with Tivo, it was one of the reasons behind the creation of the GPLv3. Tivo based their DVRs on Linux, and provided downloads of the Linux code. But their DVRs used hardware DRM to ensure that only code signed by Tivo would run, making it so that even with the open source code, you couldn't run changes on the hardware.
From what I can tell, Vizio is doing the same thing, but isn't providing downloads to the kernel code they're using. It's possible that there's some proprietary hardware drivers that they don't want to release code to, but Nvidia has already show how to work around that.
I expect the end result to be like Tivo: a bunch of archives of the open source software used in the TV, but none of the code required to make it useful and no signing key necessary to allow any changes to run on the TV itself.