A mild suggestion regarding general release of the game
Eventually the game will be fully released and publicized accordingly. At that time, you might consider raising the maximum 'level' from 60 to 80. A small-ish change, perhaps, but one that could have a great impact on the existing user base.
What would be even better would be no ceiling at all. The iMG for the next level should rise exponentially though making higher levels eventually become ridiculous difficult to achieve