Instead, the free Tor Browser will be a separate browser that includes Torbutton by default.
"We will no longer recommend that people use Torbutton without Tor Browser," Perry explained. "Torbutton will be removed from addons.mozilla.org, and the Torbutton download page will clearly state that it is for experts only. If serious unfixed security issues begin to accumulate against the toggle model, we will stop providing Torbutton xpis at all."
The self-contained Tor Browser bundle lets you use Tor on Linux, Windows or Mac OS X, and it can run off of a USB flash drive. It can be from the Tor Project's site. explains the premise in more detail.