Well above my pay grade.
I know a number of BMed pilots have already resigned- it's not a huge number, miniscule in comparison to the numbers from BACon who opted not to work for FlyBe. However, I have heard on the grapevine that a larger number are waiting to see how their applications to Virgin are going...
As to how many resignations the company have planned for, I have no idea, but I am sure they have allowed for some...
Once the dust has settled I am convinced the recruitment will be ongoing for some time to come- not necessarily in huge numbers, but a fairly steady flow.