Well, barring a POD at/bfore Amalia's birth, the marriage will still remain childless. Amalia suffered from Mullerian agnesis which prevented her having children.
That said, Otto might fare better. He originally made a play for a half-Russian princess - Sophie or Marie of Wurttemberg. However, King Wilhelm I refused, since he regarded the Greek throne as rather unstable. Sophie was later forced into a marriage she resented until she died, and Marie married both rather late and morganatically. So perhaps, something happens, and one of them ends up as Queen of Greece instead. A Greek-born heir for Othon might go a far way to cementing his relationship with the people. It might not butterfly his deposition entirely, but it can't hurt.