Belarus: I could see CPB taking over when Lukashenko isn't in charge anymore.

Burkina Faso: Their prime-minister seems to be a communist. Hopefully this means working towards a socialist state.

Cyprus: AKEL is one of the main opposition parties in Cyprus and their candidate for presidency went to the runoff election this year.

Greece: KKE is one of the main opposition parties and they keep growing.

Haiti: There are some revolutionary organisations involved in the protests against the government, maybe they'll succeed.

Swaziland: The CPS is the main opposition to the king's rule.

Taiwan: through reunification with PRC.

What others seem likely to you?

EDIT: I remembered South Africa is a candidate as well, the EFF is getting stronger