Hi Murali,
If you are planning to use Duet Enterprise 1.0 FP1 SP03 on top of lets say Gateway 2.0 SP05 onwards, you could generate OData signatures for these scenarios and use them with BDC Browser to convert into SOAP services. Then, you can use these services with SP2010. However, this direct OData->SOAP conversion is most suitable for simple entities only as BDC Browser has some limitations.
For complex entities or deep entities or you may call it deep data structures, a custom development on SharePoint side might be required. On Gateway side, you can use "create deep entity" method while creating complex odata signatures.
and of course, before all this, your development options depend on how you have installed gateway.