Ou devrait-on se retrouver?
Be careful ou and où are two different words.
Your sentence is correct, but it has a different meaning for me. It sounds like where should we end-up ? (which is another meaning of se retrouver)
Where is "should" in Duo's answer?
What is the right word order in formal question form without est-ce que. Is it, 'où se retrouve on"?