I go along with the idea that Blofeld is a man who uses multiple identities. He did so in the books - Comte de Bleauville, Guntram Shatterhand, even one we never saw him as, one Serge Angstrom. He uses these to stay one step ahead of the authorities - and in the case of de Bleauville, to buy respectability.
"Oberhauser" could be one of these identities, and I think there may be something in the idea that Blofeld has assumed the identity of the real Franz Oberhauser, having extracted everything he could out of him first before killing him or, as with Willard Whyte in DAF, "holding him in cold storage". Why Oberhauser? It might be to do with Bond - an elaborate plan to exact a personal revenge on the man who destroyed Quantum. It might be a co-incidence.
But it wouldn't necessarily surprise me if the twist in the film is that "Oberhauser" isn't the man Bond knew in his youth and that the secret referred to in the teaser trailer is something only Bond and the real Oberhauser would have known - and this proves to be Blofeld's undoing.
One other thing. In the short story Octopussy the death of Oberhauser senior is caused by one man's greed for a cache of Nazi gold. Suppose Blofeld set himself up by befriending both Oberhauser, father and son, who were themselves in search of this cache, they found it, Blofeld killed them for it and assumed the younger man's identity? Another loose connection to the Fleming source material there.