FUD Zilla reports some of NVIDIA's 28nm notebook GPUs are almost ready to enter production:
Nvidia had a big partner thing in Lisbon Portugal and some key people even talked about 28nm chips and have confirmed that some of Nvidia’s 28nm notebook chips are almost ready for production even today. Far East sources are confirming this independently.
The yields are the factor that will decide when wills this actually happen but it all indicates that 28nm notebook chips should be on time to launch with Ivy Bridge 22nm notebooks. Some of these chips might show up as a part of Sandy Bridge, but this will depend on yields on 28nm and Nvidia will try to calculate if it makes sense to launch it before.