Yup, they are supported, although they won't neccessarily be able to handle newer metadata concepts. You should certainly be able to use ones that were expecting 7.2.1 or whatever though. We have a new xml list import format that's a lot more powerfull but it's also SDK only at this point so we'll continue supporting the old format at least until that's fully integrated into the Client (and that's not that high on our list right now, so you should be good for a while).