Judeging by the good sales of The Legendary Starfy in America, I think if they made a 6th one it will be released in NA and AUS too.

Was it really necessary to revive this thread?

I think bringing Stafy outside of Japan was just Nintendo testing the waters, to see what consumer reaction would be. The game sold decently, but not enough to convince the company to bring the entire series over.

Stafy in North America was just a one-time thing, like Hotel Dusk and countless other games that Nintendo has conveniently forgotten about.