That's good news
I am sure your tech has already read this, but it might give him some ideas to read what other large forum admins have done to deal with the search problem:
http://www.vbulletin.com/forum/showthread.php?t=111239
The three things that come out of the discussion is:
-Obviously, use a separate server to serve the search queries, and only synch that server once a day or every few days. This doesn't show the latest posts, but then again those posts are much easier to find by browsing the forum directly.
-Use the fulltext search hack to get rid of the search tables created by vbulletin.
-Disable the display results by thread, and only display results by posts. This allows you to get rid of all the table joins and makes everything much faster
Some people in that discussion are running boards with 5 million or more posts as well, and they can bring valuable infos to your tech.