While reading some papers about the Turing completeness of recurrent neural nets (for example: Turing computability with neural nets, Hava T. Siegelmann and Eduardo D. Sontag, 1
When modern computers are said to be Turing Complete there is an unspoken exception for the infinite storage device Turing described, which is obviously an impossibilty on a finite physical computation device. If a computation device can do everything a Turing machine can do (infinite storage not withstanding) it is Turing complete for all practical intents and purposes. By this less strict definition of Turing completeness, yes, its possible that many neural networks are Turing complete.
It is of course possible to create one that is not Turing complete.