I've heard some spectacular testimonies to the Alpacka raft, too... Someone tipped me about this link:
Alpacka raft FAQ - cargo weight

It appears that you add more cargo at the cost of less manouverability. The issue is not how much weight you technically can carry (A LOT), but how slow the raft becomes to paddle and manouver. Not to mention what a pain it will be to carry all that gear over land. (Of course, there are numerous devices that allow cargo to roll on wheels on pawed surfaces). The packraft biggest asset is how it augments your walking backpack (or cycling) trip with the capability of using water for transport, at the expense of only a few pounds. This will work very well for a single healthy person, but not for a faimily with kids or elderly people.

Alpacke rafts are great, but for emergency evacuation a canoe with wheels to roll on may be better. Particular if you have a family with you.