Good question, and the simple answer is we don’t know!
We’d have to find lots of planets first, then we’d have to come up with some kind of way to investigate them. It’s hard enough to investigate Mars our neighbour, but the distances involved would make it incredibly difficult. Then we’d have to send a probe or something out to them and that could take hundreds of years just to get there, never mind sending any information back!
Does sustainable mean that we could live there?