I would take this rumor with a healthy dose of skepticism, there could be a grain of truth here but it could also be 100% fabricated.
Here's a brief overview of the rumors:
Via: TPUAMD Radeon RX Vega retail availability on June 5th, about one week after the Computex press conference.
There are three Radeon RX Vega cards: Core, Eclipse and Nova.
Radeon RX Vega Core is said to be a $399 card which may offer higher performance than the GeForce GTX 1070.
Next we have the Radeon RX Vega Eclipse, which is described as a $499 video card going head to head with the NVIDIA GeForce GTX 1080, or potentially being faster than that.
Last we have the flagship Radeon RX Vega Nova. This is believed to be a $599 card with performance in-line with the NVIDIA GeForce GTX 1080 Ti.