I'm wondering, are there any ways to get (and forward-reference at the beginning of the document) the total number of tables when using longtables? There are utility packages for standard table counter, but it's not used in longtable anymore starting from v3.02:
Counter for the tables, added in V3.02. Previous versions just used the LaTeX counter table, but this fails if table is reset during a document, eg report class resets it every chapter. This was changed from \newcount\LT@tables in V3.04. LaTeX counters are preserved correctly when \includeonly is used. In the rest of the file \LT@tables has been replaced by \c@LT@tables without further comment.