They’ll easily sell the 25k between Japan and Australia.
When Toyota put out a launch price offer here for the first 1,000 GR-4s, they put it at AU $39k. They expected it to take several months to a year to sell that initial first year allocation of 1,000 cars. It sold out in one day.
They released more cars in the next allocation but cheekily bumped up the price by $5k, so sales have slowed. But still, it showed the demand for it.
In Japan it will be hugely popular. Toyota and GR are kinda a big deal there, and the Yaris is a perfect sized sportscar for their narrow streets and tiny parking spaces. Also, to help with volume, in Japan they are also selling a base model with a different, low powered regular Yaris engine with a CVT, in the exact same body shell, to help homologate it. That should sell well too. Technically they just need to homologate the 3 door body for motorsport - they can put any engine they want in it.
Tl;dr I would not hold your breath waiting for the GR-4 in North America.
You may get a GR Corolla though, with that engine. Won’t be quite as good though.