The Citgo stations will find another supplier. Just as a "boycott" against a "brand" of gasoline wouldn't work, because gasoline is gasoline.
I really think it's a sign that Hugo Chavez is "overextended". and he criticized the US for "comsumerism disease".
Most of the stations are owned by independent operators. The operators will just put up new signs from another supplier and continue selling gas.
Same Pakistani, different gas.