No need to keep their citizenship (or even to ever have been a citizen) to keep Social Security. The Government will send the check anywhere in the world you want. If you paid into it, it's your's. Citizenship is not and never has been a requirement.
As for Medicare, why would they want to keep that where you still have to pay for it while Canada has that wonderful 'government-pays-all' socialized medicine that won't cost them a single Loonie? Maybe for their "Golden Years" when he needs a by-pass or she needs hip replacement, they can hop a flight to Seattle and be treated the next day rather than waiting a year or two like they do in that wonderful non-materialistic Canada.
Freak'in idiots.
They are not eligible to be part of the Canadian "healthcare" system. Visitors pay cash.
Here you go, Democrats: The Philippines are affordable, most everyone speaks English, rent, food, transportation, utilities and help (maids/nurses/gardeners, etc..) are dirt cheap, and there's even a VA hospital in Manila (though I doubt many veterans are among those "fleeing" "Bushworld")
http://www.livinginthephilippines.com/#Expats_Life