Apple released a version 6 for Lion when Mountain Lion can out that mirrored each other. Since then Apple as moved toward version numbers being tied to a particular OS and .x updates to mirror later OSes.
Safari 7 with Mavericks - Safari 6.1 (or 6.2) for ML and Lion
Safari 8 with Yosemite - Safari 7.1 for Mavericks
I think we'll see a Safari 7.2 and maybe Safari 7.3, but Apple sucks at updating old Software. Unless you plan to upgrade OS X you'll eventually want to switch to Chrome or FireFox to get the latest technology.
I really dislike the way the newer versions of Safari does not refresh web pages when using the back functions so I'm stuck at version 7.0.6.
When reading forums such as this one I prefer that when reading a post and then returning to the forum index that the posts I've read become un-hilighted.