Whereas the original GeForce GTX 1660 packs 6GB GDDR5 clocked at 8Gbps, the upcoming GTX 1660 SUPER reportedly has 6GB GDDR6 clocked at 14Gbps.
Then there's also a rumor about a GeForce GTX 1650 Ti:
NVIDIA is also expected to add GTX 1650 Ti to 16-series lineup, although we cannot definitely confirm this launch just yet. Chinese ITHOME claims that the launch of this particular SKU would happen on October 22nd, but there is seems to be a confusion regarding the memory configuration this model would feature.