If i import the sources from ancestry.com into FTM, what will happen to them if i cancel my subscription, will they all be lost?

Your sources and images will be intact if you merge them into your Family file that is stored on your computer.

REgards,

Make sure you save any images if there are any or you won't be able to access them again if you cancel your subscription. I've cancelled subscriptions several times and I have all my data and images intact so you shouldn't have any worries there.