too much?

Do you think it is possible to run a 50 miler mid June and another in the end of August or is this too much? It would be 10 weeks between the 2 races and I will train using a run/walk method to reduce chance of injury.

Lots of runners run 1-2 ultras per month and just stay loose during the mid-week workouts (a speed session, cross-training, etc.). No, there isn't any reason if you are healthy and in condition that you can't do these two races. Listen to your body would be my advice.