Both these men were critical parts of the World Cup winning team. If England continues acquiring such players, they will surely become a lot stronger and become a bigger challenge to teams like India and Australia in the future.
Imagine an Irish team 5-6 years back, with Morgan, Joyce and Rankin along with those who stayed loyal to Ireland (Kevin O'Brien, Dockrell, Stirling, William Porterfield.etc). They would have been one of the stronger sides outside the big 3. BTW, I won't complain much about Ben Stokes. Although he was born in NZ, he moved to England when he was 12 and it was the English domestic cricket which was responsible for his rise. Morgan played for Ireland until 2009, and he moved to England only for better opportunities.
BTW, I am watching the Netherlands vs Bermuda match right now. I can confidently say that Netherlands will be playing in the next year's world cup, as they are in a very comfortable position right now. They have made a massive 206/3 after 20 overs, with Ben Cooper, Max O'Dowd, Ryan ten Doeschate and Ackermann smashing the bowlers all around the park.