Earlier this month, Google made it possible to export a single wave as a Zip file. Google now, also let you select up to 10 waves in your search panel and download them all together with the same options.
"We hope this feature proves a useful way of saving the information that you have in waves. In addition, we're working on ways for you to access waves through Google Docs and as announced back in August, we'll continue to keep wave.google.com running at least through the end of the year," stated Google.
How do I export my waves?: