I don't think that he would really dump it because many investor could lose interest and leave the project.
If that massive amount would be dump the price would crash down big time it is already low so it could destroy it.
Obviously he wont be doing that, Justin sun have good hand in marketing & may be he will use & allocate maximum amount out of this unlocked 33B token for TRON Platform development & there will be some token burn as well out of 33B TRX Token.