From the ADO.NET team blog Oracle client to be deprecated in .Net 4.
I must say I can understand why. When I was doing Oracle I usually used the Oracle Data Provider for .Net (ODP.NET). It was more up to date and supported more of Oracles advance features.
Hopefully this will give Oracle a bit of a kick to get them to release new versions of ODP.NET when new versions of .Net are released, instead of 6 months after a new release has come out.