I changed the design of a site, but

I work at a company that is changing its brand. So I changed the entire design of the site, which was going to be published today. But they changed the date of the rebranding and now it will happen in just a few weeks.

My problem is: the site needs to stay with the old look until the official rebranding, but the company needs to publish new posts until then. I want to know, if there is a way to publish new stories without publishing the whole site.