AMD allowed Intel to remain uncontested in the high end desktop CPU space for several years. There were no excavator or steamroller updates to the FX line. Piledriver remained the high end until AMD was able to launch Ryzen last year. AMD wasn't going to make those processors and then sell them at the price they would need to be at to be competitive with Intel's offerings. I imagine we'll see a similar track with Vega. It will remain the high end GPU until the GCN architecture is replaced in 2020. We may see 7nm vega updates in the mobile line and APUs (see steamroller and excavator), but I doubt we'll see discrete RX boards.