The announcement was made on Twitter.

And KaiserNeko has made a full article regarding the situation

This is a sad day indeed.

I will say this though; Thank You TeamFourStar for all the laughter and memories with your humour. I’ve enjoyed the ride and though there will be no Buu Saga, your ending to the Cell Saga was perfect.

This is really disappointing, I suspected burnout and was partially right though copyright considerations seems to have factored in this heavily as well which is a real shame.