The 2GB RAM will make next to no difference for most users. It would matter only if you were running very heavy skins or had a massive media database (10s of thousands). 16GB storage similarly will make no difference to how people use the product.
At the moment the version of OpenELEC (actually latest version is LibreELEC) on MiniMX is stable and runs excellently. It's the result of 6 months of work. Any successor would have to have a similarly stable version of LibreELEC available for it and be a worthwhile performance / feature increase vs our MiniMX.
Amlogic S905X is an interesting chipset because it promises HDR10 at low cost, but it will be months before it's working with LibreELEC. We may stock an S905X product before Christmas, and if we do we'll choose the one with best LibreELEC firmware.