The number behind Ultra is pretty much the same as with the i$x scheme. 3 is entry, 5 is mid range, 7 is high end, 9 is bad decision making.
The number after that kind of works like before. So higher number means more better. Probably with an extension for coming generation. Remember, the first i5s had 4 digit names as well, the fourth digit was prepended to indicate generations.
Thing is, there's no really good naming scheme, because there are so many possible variants/dimensions. Base clock, turbo clock, TDP, P core count, E core count, PCIe lanes, socket, generation ,..... How would you encode that in a readable name?