Is it permissible to delay selling gold given as charity—for the purpose of distributing its price among the needy—while awaiting an increase in its price?

As long as the gold remains in your possession, it is not considered charity (sadaqah); rather, it is merely an intention for charity. There is no harm in keeping it and postponing giving it as charity until a suitable time, unless it is zakat and the time for its obligation has become due, for zakat is immediately obligatory.