Prepare to be astonished, then. People were saying the same thing around the time the Radeon RX 480 launched, that for sure it would be a hard launch at Computex:
http://www.pcworld.com/article/3073...laris-gpu-updates-and-bristol-ridge-apus.html
That turned out to be a bust.
Launch dates of the past three GPUs from AMD:
"Polaris" AKA Radeon 400 series: June 29, 2016
"Fiji" AKA Radeon Fury series: June 24, 2015
"Grenada" AKA Radeon 3xx series: June 18, 2015
You may hear additional details about Vega via AMD livestream at Computex. You may even see a few carefully curated, canned demos and be promised that it is arriving soon™. I would not expect a hard launch of Vega before mid June because that's just setting yourself up for disappointment.