Unlikely.

The caulk that is on the capping is probably brittle and photo degraded at this point. Removing it will be difficult and it is much more likely that the capping will damaged in the process.

Most caulks have an adhesive component to them and getting that coil off of the window is probably going to be tricky without damaging it.

Can't hurt to try but I would not hold out hope.

I agree with Windows on Washington. Putting brand new windows in and leaving the old coil and caulk is a little like buying a brand new car and using the tires off the old car. If you don't feel comfortable doing the capping, you can contact a company that does siding and get a price from them. It usually runs somewhere between $50 and $100 per window depending on size and complexity but would be worth it IMO.

I agree with these responses. Your chances of getting the window out without damaging the external wrap is virtually nil. However, when pros install windows in this area, they routinely wrap the outside with new aluminum coil. It's part of the installation price -- so be sure your installer understands that that's what you expect him/her to do.