Installing WPMU in a subdirectory then copy it back to root on relaunch day ?

Hello,

we have a currently live website that we want to keep online until we we developed the WPMU relaunch site. The WPMU setup is to create the subdomains per URL not as a subdomain ( test.test.com)

We installed WPMU under a Subdirectory and are thinking that at relaunch day to move the WPMU supdirectory to the root ...

what do I have to watch out for ?

I am assuming that i will have to adjust the htacces file to the new directory (root) instead of the subdirectory am i correct ? and are there more things to watch out for ?

Thanks in advance

Marion