That's the assumption, but from what I understand the planning application that's been submitted has no reference to safe standing sections.
And as has been posted and re-iterated countless times on this and other forums the current thinking within the authorities - H&S, police, footballing and governmental - is that if/when safe standing is permitted, it's almost certainly only going to be on a 1:1 ratio - one seat out, one standing position in, so a 52,000 seat stadium will become for example 46,000 seats and 6.000 standing = 52,000 capacity.
The club, or more correctly the previous Deputy Chairman Keith Harris, suggested possible expansion from 52,000 to 60,000 but, no explanation of how this would be achieved has ever been forthcoming.
Furthermore, Dan Meis, the architect has suggested BMD will be a one-off build, with practically no scope for physical expansion to accommodate a larger capacity... and he personally doesn't advocate building BMD to more than 52,000 either.