The Open Skies agreement is EU-US, so any EU airline have the ability to start a route from any EU airport.
I agree that I see EY using EI as extra access to EU airports that they are currently restrained from entering. They already have AB in Central Europe, EI will cover the UK and onward to North America. These options could offer them more access (indirect) to the EU than EK will have. I am pretty confidant that we will see EI operating to Canada within the next 2 years.
While QR and EY are growing slower than EK they are still growing. Those 3 airlines may well be the heavyweights of the next 10 years as existing 'legacy' carriers struggle to adjust to a changing world aviation market.