The WTS will never sign up, nor were they ever going to...
...(capitulating to any pressure from "Satan's World" this close to the End notwithstanding), to do so would be tantamount to admitting there was/is a problem and that they are culpable... and they'd rather gargle with battery acid.
They'll try and spin public shaming (of failure to join) as martyrdom and the loyalists will probably buy it, but that's to be expected... anyone with half a brain will realize that it doesn't even come close to, say, arrest and imprisonment for their convictions (i.e. the real deal).
There's no guarantee that financial sanctions will be effective, since WTHQ had the bulk the Aussie savings transferred out of the country a couple years back (super-likely in anticipation of this very issue, which indicates that they never intended to join the redress scheme from the beginning)...
...but...
...loss of tax-exemption?
That might actually make things difficult, in no small part because...
a) ... I strongly suspect that the Org's business model has become highly dependent on it's charity status, and...
b) ...how the fuck do you spin "paying back Caesar's things to Caesar" as "persecution"?