I’m hoping it turns out to be a good thing. As corporation taxes seem to be higher in the US than they are in Oz, I don’t think they;re doing this to save money… so it seems only logical that they feel this will increase sales. And unless their business model changes, more sales for Envato means more sales for Envato authors.
It may not seem apparent to us now how their (only publicised) reason of more payment options is going to have any kind of massive influence on sales, but I’d be very surprised if they’ve not ‘done the math’. It’s unlikely the Envato management team were in the pub one night and just said “Hey, I’ve had a crazy idea… let’s go to the US! Woo-hoo, party! Taxes?! Taxes shmaxes.”