When implemented, it'll look something like
View attachment 95457
If a change in the law allows the seats to be retracted for domestic games, it will almost certainly start with a 1:1 ratio. But, in theory at least, you can get two people in each space behing each rail. It'd be very cosy, and I can't say I'd fancy it, but it's possible.
In Germany, rail seating areas, when used for standing, tend to operate on ratios of 1.2:1 to 1.8:1
Realistically, if we did something similar at Bramley Moore, we'd be looking at a ratio of something like 1.5. I forget the capacity for the opposite stand, but the main stand behind the goal will have a standard capacity of 13,000, so a 1.5 ratio would add 6,500 to that. Taking it up to 62,000 only needs an extra 3 or 4k at the other end.
My understanding is that both stands will be, in terms of things like concourses, toilets and general egress issues, designed to cope with the extra capacity.
Obviously, if money gets tight, they might not put everything in place to support the extra capacity from day one, but there should be the square metres required to do so at a later date.
Whether or not it'll ever get expanded by 10k by using extra capacity provided by rail seating is another thing entirely.
My personal view is that, some time in the next five to ten years after we open, is that we'll see an increase in capacity down to squeezing more people into rail seated areas, but it won't involve all the areas in the South and North stands.
So I reckon we'll open at just under 53k, and see that, in the fullness of time, increase to something like 58k as the lower or middle areas get converted to expanded standing.