Hi,
Yes this is possible. Just open JoomSEF's URLs Manager and in the toolbar select "All Filtered" and "Export" in the select boxes and then click the Proceed button. You should be offered with an SQL file with all your URLs to be downloaded.
To import them again just click the Import button in the toolbar, on the page that opens select the file to be imported and click the Import URLs button.
Please note that only SEF URLs with their meta tags can be exported. Associated Aliases and Internal links as well as 301 redirects can't be currently exported.
You should also backup your old database so the URLs can be restored manually in case the export/import doesn't work well.