Being wary not to feed the trolls, and going back to the original post...
I don't think there is any danger of this happening all the while there is any involvement of the private sector in the industry, because it wouldn't be long before the market forces that led to drivers wage increases in the first place came back into play and wages started to go up again. If it was fully renationalised then I can see it being attempted for sure, but otherwise no.
One of the biggest challenges around any possible future renationalisation would surely be harmonizing pay and conditions across the country. There are TOCs now that were formed of previous TOCs where they haven't been able to harmonise after years. It would need full renationalisation and harmonisation in order to be a success - otherwise people would still leave for the better paid TOCs and the others would have to try to keep up - as has happened since the 90s - leading to the drivers wages you see today.
The next issue is how do you harmonise grades within the industry? Speaking for drivers (but it could be applied to any grade) you have some TOCs offering over £70k basic while others are still paying in the high £40k bracket. Meal breaks, rostering, sundays, DOO, duty length etc all vary between TOCs so you've got to factor that in too. There is huge disparity within the railway industry among people who do the same job. You could cut £20k from some drivers wages today and they'd still be earning more than drivers at other TOCs.
I wouldnt be against harmonisation of the grade nationally, but the only way it's going to happen is with full renationalisation. Whether or not it's a race to the bottom, a race to the top, or a meeting in the middle (and how the hell it would be implemented) would remain to be seen.
If it was nationalised then you would have to think of ways to keep drivers working at depots where the work is absolute rubbish. In BR days the metro depots at my TOC were very different to what they are now. If a driver stays with one intensive TOC because he's a prisoner to his higher wages, or his safety record holds him back, he'd no longer have any reason to stay so they'd need to look at other ways of balancing staffing (eg: completely changing the work content at some places).
There would be countless other things to consider too.
It's easy to spout the same tired, jealous rhetoric about drivers wages and unions, its easy to ignore the fact that this narrative is overly simple... but it's not helpful, it lacks originality or serious thought, and doesn't actually achieve anything unless you are going to offer workable solutions to address the massive disparities within the privatised rail industry.
Would I be prepared to accept it? Not without a fight. Would you let someone come round your house and take your stuff without a fight? No, of course you wouldn't... Or maybe you would? But I wouldn't.