I've managed huge teams, and counseled managers of even larger teams. The question the OP asks is a good one: if I'm an employee of DSR and I see all these changes, won't I be nervous?
The answer is yes, _IF_ the managers of DSR don't handle it correctly. But if they do it right, and sit down with the others and explain the situation, why each person left, how the situations were each for their own reasons, how they are valuable employees and don't need to be worried about their jobs, and that this isn't some kind of wholesale layoff, everything should be fine.
Don's run a company for years, I'm sure he's a smart guy, and I'm betting he's got it under control.