It's hard to say what will happen. Going by the past history, I think it's a safe bet that the first Vega models will be high end. So AMD will sell the RX line as their entry level to mainstream products, with Vega being the top of the line stuff.
At some point in the future, when the RX line has run its course, they may then bring out some lower end Vega models. Of course it's impossible to say how low end those will be or what their price points will be.