According to Notebookcheck, NVIDIA is planning a cosmetic update in its lowest-tier segment of mobile graphics cards.
GeForce 920MX, 930MX, 940MX
The lowest tier usually means lack of GTX prefix. These cards however lack even GT affix, which indicates even slower chips, often dedicated to multimedia playback, rather than gaming.
The specifications of new graphics cards will be similar to currently offered GeForce 920M, 930M and 940M. New chips are said to receive GDDR5 support, which would drastically improve performance compared to DDR3 memory they currently use.
Notebookcheck compare existing GeForce 940M DDR3 model to recently released GeForce 940M GDDR5 used in Microsoft Surface Book. Gaming performance increased more than 20%, just by updating DDR3 memory to newer standard. We should expect similar boost from new GeForce 900MX chips.
Notebookcheck promises to update their database with MX GPUs benchmarks as soon as those become available.