Yes it is.
Login into in my Cloud.ch with you current email address and password.
On the top right corner click on your profile's avatar
On the drop down menu click on Settings:
If your myCloud is connected to a Passeport Account please click on the next page on edit profile:
Otherwise if your myCloud is connected to a Swisscom Login please click on the "Change" Link:
If you use a Passeport Account you will land on a new page where you can select your new email address by clicking on change as illustrated below:
Follow the instructions from there.
If your using a Swisscom Login your able to directly edit or modify your "Contact E-Mail Address" in the up following input field: