We'll get more than one more regular set before 18+. The webmaster will not only have shot additional sets that he'll want to use all of, it's going to take more than a single week to shoot the new content and convert the site to 18+. While it's legally possible to just add the new sets to the existing site, most billing companies won't touch a site with mixed adult and under 18 content. And as soon as the first nude photo gets posted, he'd need to have the 2257 information on file for every single pic and video on the site under penalty of ugly fines, even the NN ones already up. Most webmasters don't do that paperwork for the non-nude sites since they don't need to at the time, so any content without all the documentation would have to be pulled. It generally isn't worth the fight, setting up a new 18+ site is just plain easier. Webbies don't take on the expense and hassle to create whole new sites for models turning 18 and going to more adult content just because it's fun, the alternatives are simply worse.
Even if they shot a ton of content this morning, the first day it's legal to take straight-up nekkid pictures of Alex, I suspect we won't see any 18+ material (except maybe some teasers posted somewhere other than the main site) until mid-November. With Thanksgiving coming up, it may take all the way into December or later. If memory serves, they were none too speedy to get the 18+ Amanda Verona site going, either.