I don't think there's much chance retirees will be able to get LPR status, but they may eventually come up with some sort of residency permit like they have in the Cayman Islands.
Most non-immigrant categories require proof of abode abroad, so there aren't many options really.
Belize seems to be popular with retirees lately, I'm assuming it must be possible to stay there year round. The Bahamas have a fairly simple residency permit system but they have really high import tariffs. Not a problem if you live and work there because there's no income tax but as a retiree it makes things difficult.
Steve.