I feel like there's a good chance Disney won't let it get that long before they close the SB line to avoid posting 5+hr wait times. Maybe after it hits 120 or 180 mins they will turn people away and tell them to come back later.
If they leave it to guests to self regulate, it will be a long A** line.
Considering pre-pandemic, FoP had posted wait times as high as 250-300 minutes in some cases even exceeding 300 minutes, I wouldn't be surprised if Disney allowed RoTR's standby queue to get just as long. But if they do start to turn people away at a certain time - wouldn't that be similar to people who couldn't get a virtual boarding pass? Except if you do get in line, it comes with a 4 hour wait...
The number of riders that can ride RoTR per day is still the same (assuming no breakdowns) - so some people will still miss out on riding it. The big difference is going to be - if you get in line when it is really long - you won't be able to do anything else, with the virtual queue at least you had the option of doing other things.
In terms of being "stuck" waiting for your boarding group - I suspect the same will happen with the standby queue, the difference is instead of being stuck in Hollywood Studios, you'll be stuck in line.
I really don't see how this adds flexibility as Disney is stating. The only flexibility is - you can choose to wait a really long time, or choose not to. With the previous system, you also had the same choice - but because your wait time was usually much shorter - everyone wanted to try to ride it.
I don't necessarily see rope dropping being any better either, if you're lucky and get there early enough - I suppose you can ride with a short wait, but for the majority of people - even if you rope drop, you still may end up in a 2-hour or longer queue.
Now if you want to rope drop and ride something other than RoTR, I can see that being a big advantage now, since most everyone will run to RoTR and you can probably hope on the other rides with little to no wait.
It will also make the rest of the park less crowded since RoTR will suck up tons of people - so if you're not planning to ride RoTR, it is mostly upside for you.
Once Genie and IA$ launch, it will probably be an even longer wait since the standby people will have to wait to allow the paying customers to ride first.
I hope the "pause" on the virtual queue is short lived imho.