just my take on the situation. not too long ago i speculated that MS would be looking to improve the Series S in a couple of possible ways. The simplest would be to increase its SSD from 512 to 1tb. Basically the drives used in the SX would now be used in the SS and the SX would also get a bump in capacity to 2tb thanks to larger drives being made in the smaller form factor. this is inevitable as we have see HDD sizes increase over the life of the 360 and XBO respectfully.
The other option to improve the SS is to up the internal RAM from 10gb to 12gb. As small as that may seem... it's that 2gb difference that is really keeping the SS from running One X enhanced software even though the other specs of the SS exceed the One X considerably. The CPU is better, the GPU is more efficient in 4tf vs the older 6tf of the one X but the area the SS cant make up the difference is the ram. I mean if MS were to utilize virtual memory tricks (using ssd capacity as a portion of extended memory) of the old days, it still doesn't make up for the lack of one x enhanced capabilities that the SS is capable of doing.
If MS are planning to revise the series line then expect it to be the former that i mentioned (SSD capacity changes) rather than the latter. Although if they could give the SS 12gb it certainly wouldn't hurt and im sure devs would like having 12gb / 16gb split instead of 10gb / 16gb currently.