Taking knowledge from the 2005 E/bound repo which has had history repeated so far with the 2008 repo, and in the knowledge there are so many GTY rooms allocated, I would say they will now be allocated after 90 days out before 30 days out.
Firstly in 2005 there was also a considerable number of GTY rooms, they all traveled, so no panic.
Like 2008 the odd one or two staterooms came up for sale now and then.
Some more came up for sale just after the 90 days pay up mark.
I purchased a Cat 9 first, with a stateroom number later upgraded to a CAT 4 GTY, I had my stateroom given to me, about 60 days out. I first saw it on the DCL website.
GTY gives DCL maximum flexibility, some people might for example be penciled in for an upgrade, but others might wish to pay for an upgrade. So it allows them to swap about rooms.
Also some people might want connecting rooms, some people might cancel and if they allocate a room now, you might 'block' a connecting room so they have to move again.
Now, with so many GTY's issued, if they started allocating room numbers to a few, the rest of the cruisers would bombard DCL with requests, why not me?
So to be fair it will most likely be after 90 days, unless they can wave a magic wand with pixie dust and make everyones dreams come true, ,,,well its Disney.