Moldova and Romania speak the same language and reunification has been a possibility since independence. This Jan 2022 article quotes a poll finding 44% support in Moldova for union with Romania.

That was before Russia invaded Ukraine. Romania is in both NATO and the EU, so by joining Romania, Moldova could essentially shortcut the membership requirements for both organisations at the cost of giving up sovereignty. This bargain looks a lot more attractive now that the perceived risk of Russian invasion is higher. I note Metaculus already has a question on whether Russia will recognise Moldova's breakaway region Transnistria this year.

Will Romania unite with Moldova before 2025?

Positive resolution will be based on an announcement of a union by both relevant governments, effective on or before 1st Jan 2025. Union here means that the two countries become one country. If Romania unites with Moldova but excludes Transnistria and/or Gagauzia then that still counts as a positive resolution.

• From Metaculus