In around 2020, a severe pneumonia-like illness will spread throughout the globe, attacking the lungs and bronchial tubes and resisting all known treatments. Almost more baffling than the illness itself will be the fact that it will suddenly vanish as quickly as it arrived, attack again and then disappear completely,
I don't believe in merging, but the proponents of the doctrine of oneness certainly do:
However, suppose we are still quite far from an ultimate theory - then it makes good sense to accept theories that aren't quite right if you look hard enough. For example, the ideal gas formula PV=nRT was a really useful discovery, but it obviously breaks down badly at temperatures close to the point where the gas in question liquifies, and it breaks down at very high pressures because of inter-molecular forces and such like. I guess this was considered less of a problem because scientists back then didn't think their new theories were ultimate theories.
A Dualistic theory could then be embedded in an Idealistic framework when appropriate - just as Newtons laws of gravity and motion are embedded in GR.