| I think you're mixing terms - or at least I've never heard of Inner and Outer magic users (Other than Thieves having Inner Magic, which is a rather different creature). From context I assume you mean Magic Primaries and Magic Tertiaries.|
Terminology aside, the answer is no. It is intended that the three Magic Prime guilds each have a High Sorcery spellbook that is intimately tied to their confound. They will not be shared in any way outside of their own guild. (In the case of Teleologic Sorcery, since that's the only on that's live, many of the spells simply wouldn't be functional if cast by a Trader even if we did let them cast them).
There are also no plans to add additional High Sorcery spellbooks or Empaths.
There are plans to develop the low Sorcery spellbooks which will be open to everyone (Lay Necromancy, Feral Magic and Low Sorcery).
"Ever notice that B.A.'s flavor text swells in direct proportion to how much one of our characters is getting screwed?" - Brian Van Hoose