Who cares what coinbase is doing? It's just one exchange out of many. I have never used them and aren't planning to. I'm happy with my local exchanges.
Bitcoin won't get centralized with 2x, it's FUD.
Coinbase is one of the largest exchanges in the world, and is growing very quickly. They have more VC funding than any exchange in the world. Their actions are far more relevant to Bitcoin users than most other exchanges.
Personally, I was very concerned about Segwit's 4x block weight increase, and I think we may see that it does have a significant centralizing effect on its own. All past research suggests that larger block sizes cause centralization, and it's completely logical. More throughput = higher broadband costs and higher orphaning rates. Those are centralization pressures.
An 8x increase could absolutely cause significant centralization. The extent is not entirely clear, and that's partly why we should not move forward with it.