Okay before I start on this news-item, I really need to state that this is based on a vague rumor, nothing has been confirmed or denied otherwise. Here's the story, some reports say Polaris 10 can't hit 850 MHz reliably and that availability will be pushed back to October. I sincerely hope the rumor is not true.
The news arrived through Nordic Hardware saying that AMD's partners "won't have any new cards to display at Computex and the only Polaris cards promoted to them from AMD are R9 390/390X performance class but for a mid-range price. Reports say Polaris 10 can't hit 850 MHz reliably, whereas Nvidia already demoed the 2000 MHz marker with their GPUs.
A board partner response seem to be "as of now, no information".
Rumor indicates that this info is backed by a rather large AMD partner, that there will be no Polaris-based video cards from AMD partners at Computex. That means no Polaris on Computex and no availability of the cards shortly thereafter (if this is true).