Kathy,

It seems that you feel the clause:

that the thoughts of many hearts may be revealed

is somehow still referring in some way to Mary. But the statment to Mary is a "parenthetical aside" associated with the first two clauses, and has no bearing on this final clause.

Read without the parentheses, the thrust of the passage is entirely about Christ:

Behold, this [child] is set for the fall and rising again of many in Israel; and for a sign which shall be spoken against; that the thoughts of many hearts may be revealed.

Compare Romans 2:16:

... in the day when God will judge the secrets of men by Jesus Christ, according to my gospel.

In Christ,
Paul S