That would've been a bit rough on the FOs, wouldn't it? Having to go back to being an SO sitting in the back for another few years...
The loss of the 767 and the almost simultaneous reduction in numbers on the 747 resulted in quite a lot of people taking a redundancy package. Many, possibly most, were able to keep their rank, but they needed to have sufficient seniority to access any particular slot on the other aircraft types. The movement of people was across most fleets. Many 380 FOs lost their slots and had to go to the 330, and some of them also lost a bar, but were able to stay on the 380.
Losing any position that you've put a lot of work into getting would be upsetting. At the time though, it looked as though the most junior SOs could even lose their jobs...that was only alleviated by the number who took the VR.
(I was going write "twiddling their thumbs" but I guess that they still have meaningful work to do in that role.)
That's the problem with the SO job. Outsiders think they twiddle their thumbs. You can do an awful lot of work without touching the controls. There are times when supporting is actually harder than the actual flying.
JB et al., would the downgrade from FO to SO mean the person would also then be on long haul routes only? Or are SO's also used on some short hauls?
SOs aren't normally used on shorter flights, but they may sometimes be required by flight time limitations. They're only on the long haul aircraft types.
A scenario that could conceivably appear in the future with the loss of about half of the 747 fleet planned would see their Captains, FOs, and SOs use their seniority to move onto other fleets when their aircraft are retired. Looking at the Captains for instance, a substantial number are senior enough to displace on to the 380. That means they'd push 380 Captains out of their slots. They in turn are all senior enough to displace on the 787 (or 330). The push continues until we get a Captain who'd prefer to go to FO 380...and then so on. Very, very, messy.