my speculations:

6.4 will be the last a6 update. i hope/guess octrees, the new terrain/model features and the light management will make it into that final update.

the main features of a7 at the beginning of its life cycle will be lite-c and a new much more modern wed interface. wed will use the engine for displaying the 3d view and maybe incorporate the announced interactive template editing. later a7 will get stuff like weighted bones, a shader editor, improved stencil shadows with multipass rendering like in doom3, depth map shadows as an alternative to stencil shadows, the planned game starter,...