By the way they said "UT3 will be required to use the expansion" makes it sound like it will cost money for sure. If this expansion doesn't have a spectate tab, new GUI/UI, announcer voices, fixes, and new Non Warefare / VCTF game types, no way will I buy it. Something tells me the expansion will be deader than the vanilla UT3.
Not only do new customers have to buy UT3 but they have to buy the expansion now to. Some of the current players of UT3 will probably purchase the expansion while the new customers just pickup UT3 which will further thin out the amount of players online; I wonder if people with the expansion installed will be able to join the UT3 vanilla servers.
If the UT3 expansion was a stand alone like UT2004, more players could buy it without the need to buy UT3. I think this method of releasing an add-on that requires UT3 to be installed isn't the right way to bring in new customers.
But yeah, if the same exact GUI/UI remain when the expansion is installed. I will not buy it for sure.