I'm a month late on this news...
System.Data.OracleClient Update
http://blogs.msdn.com/adonet/archive/2009/06/15/system-data-oracleclient-update.aspx
So, how does this effect Mono? Hopefuly None because this is the only way to connect to oracle using Mono other than ODBC. So, I and others will try to keep maintaining it.
Oracle's own ADO.NET provider does not work on Mono, and Oracle has said they will not support Mono. To be honest, I don't think ODP.NET works that great on .NET either.
I've always preferred to use Microsoft's provider for Oracle. This is true even for ancient applications written in Visual Basic 6 - I preferred to use the ODBC and OLEDB providers for Oracle from Microsft. The Oracle database providers written by Microsoft were far more STABLE then the providers/drivers written by Oracle for their own database.