TV firmware has substantial differences from the players, and between different brands of TVs, so you can't reference one version for the other. To my memory, this is the first I've heard of a Roku TV experiencing audio dropouts. I have two, and both are used daily. I haven't had any audio issues with either. Just to show you there are differences between products, my Insignia TV (24" 720p set) is on firmware version 8.1.0 build 4140, and it's been on that version since July according to the update screen. I can't compare it to my Sharp, as that TV is in the beta group and might not be on a production version.
Of course not. You should expect your issue to be addressed. They have just rolled out a fix the the Roku players that appears to have resolved the issue for them. I can't say if they were aware of a similar issue with Roku TVs, but with this fix under their belt they should be able to address the problem with the TVs much faster than they did with the players. I know they are testing firmware updates all the time, but I can't say if this issue is currently under test. I'm not a Roku employee, just another user like yourself. I was just pointing out that version numbers between the Roku TVs and Roku players usually don't match up with each other.
Those of you experiencing this issue, we've just enabled manual updates for 4640 models that should fix your issue.