Any ideas on how long this type of thing lasts, if we
will get what meager rankings we had back, or if we
will be starting over again?

Google Dance is a term long abandoned as Google doesn’t do a major "dance" anymore but more frequent updates. This year alone, webmasters have reported seeing significant changes in Google SERPS in February, and now in March

Yes, many webmaster forums are reporting changes in Google SERPS for March. Read the WebmasterWorld.com discussions on Google changes this month, many of which are reporting to be slapped with the "950 penalty" or keyword penalty http://www.webmasterworld.com/google/3269317.htm