When Sanex decided it wasn't going to stay on as title sponsor, the WTA went a different route, opting instead for regional presenting sponsors. They figured it was too confusing for new fans to adjust to a different name every few years. Corel WTA Tour, Sanex WTA Tour, (Sponsor Here) WTA Tour, not to mention having to change the URL of their website, putting all the redirects in place, having to contact sites like Yahoo to change the links. (Not to mention some of us having to update email contact addresses.) Not to mention how it could complicate ongoing negotiations if their name keeps changing.
So it will be easier if it's just the WTA Tour. They are looking to sign presenting sponsors in each region of the globe. Porsche is the North American presenting sponsor. And the money the tour is getting from Porsche is only $1 Million less per year than they were getting from Sanex. So they stand to come out ahead financially when the other sponsors are in place.