Some of this has been confirmed.
It has been confirmed that your dice pool = x + 1d6, where x is equal to the number of mastery levels on your side of the board.
The most common rumor is that while you need 4+ for a die to succeed on the cast, you need a 6+ for the die to succeed on the counter, but mastery levels, wargear like psychic hoods, special rules like Adamantium Will, and having a psyker near the caster will all modify that number.
Agreed.