Is there a use case? The S905 is already quite bandwidth depleted and the S912 doesn't do much on that front (it's still 32bit bus width to RAM and DDR3). One can argue having more RAM may be of use but extra cores will probably overheat more than anything else.
It'd be interesting to have an SoC running shrunk A53 with clocks closer to 2GHz and 64bit DDR4 DRAM bus. Bigger caches are also a necessity if these are to become interesting for web browsing and general desktop use.