Similarly the BeOS platform morphed into Palm OS 6 (Cobalt), which only ever appeared in sample quantities from a phone OEM. (This was well after Palm spun off their OS business, but before PalmSource was acquired by ACCESS)
...and then technology from Palm OS Cobalt, the Binder, migrated with engineers from that team to become part of the low-level system interface in Android.
The problem is that anything could have much more mindshare. WebOS has negative mindshare; a new product built from the ground up with modern technology actually has a better chance of success (and indeed, that's likely to happen).
I wouldn't be so categorical about that. There's at least a minority of users, most of them technical, that really appreciated WebOS for its capacity for multitasking and the UI, if nothing else [1]. (How relevant would this be in a TV OS is debatable.)
Even today WebOS remains a good platform for hacking with an unofficial app marketplace [2] that's still actively maintained and offers, among other things, two "real" Linux distributions (Ubuntu and Debian chroots). I keep a Palm Pre Plus with Debian myself for use in various experiments (like making a time-lapse camera). I got it for cheap when it was clear that WebOS is in decline but now I (along with many others who did the same) would be in the market for a new WebOS device if one came out, though probably not a TV.