When will platform 15 be widened? When St Thomas St entrance opens in the summer?
Things change in August when the lower concourse opens, however maybe not quite in the way most people think from reading the signs that say the platform is only temporarily narrow. It's a little white lie.
P15 is already plenty wide east (country end) of hoardings around what will be the stairs/escalators void down to the lower concourse, the problem is the rather narrow (two person width) bit which runs past where the stairs will be.
There is a bit of extra space west of the stair vault to be revealed when the hoardings come down, but the narrow bit will remain about as narrow as it is now.
But things will improve because right now everyone has to pass this area as everyone uses the upper concourse gateline, hence it's very congested, hence the cattle pen. When the lower concourse opens they expect most people to use the new stairs and go straight down there so it won't be a problem as this narrow area will only be responsible for about 1 carriage-worth of people stepping on/off the train and a few people passing to get the bus.
At least that's what I've gathered...