The following is promised as part of support at this very minute. The SVN access described has not been provided for a very long time. Sencha's development has transitioned from open source to a black box as far as their customers are concerned.
Access to Development SVN
Test bug fixes, preview new features, see every code checkin through direct access to the SVN HEAD.
Would you like to verify that the next version will indeed fix the bug you reported? Would you like to experience a new feature before it is officially released? Your paid support subscription gives you access to the SVN HEAD. This means you will have early access to test bug fixes and new features. Since you will be able to see every code checkin, you’ll know what will be coming in the next release.