1. Radical modernisation and internal democratisation, so that the PCRM becomes a modern social democratic party. This would involve tossing out the entire old guard - Voronin, Misin, Stepaniuc, Calin, Ostapciuc etc. Remember also that Marian Lupu's Democrat Party already occupies this political territory. In all it would be a very difficult scenario to pull off, but the only one that would give the communists a future as a party with a broad political base.
2. Head back into old-fashioned Marxism-Leninism. It would have to toss out its capaitalist wing and anyone who smells too much of money, and find a true believer (Isaev?) as a leader. The party would gain political credibility, although its support base would shrink to around 10% or so. It could, however, be a junior partner in left-leaning Democrat-led coalitions.
3. Rebrand and position itself as the party of the Rusophone electorate. In this scenario they would really only have to get rid of Voronin, I think, together with one or two people like Stratan who are too "Moldovan". This would probably give it a share of around 20% of the vote, and, if it is moderate and plays its cards well, it could be a junior partner in most future governments (as the ethnic Hungarian UDMR is in Romania).
4. Gradually descend into oblivion. If it fails to clearly make one of the three choices above, the PCRM will gradually see its electoral base stolen by other parties or die off due to advanced age. It will be riven by internal tensions which will result in factions splitting off and going their own way. Over the course of the next decade the party will shrivel up and disappear.