I like to think so. It's an interesting thing to speculate on.
I saw that and i was like, hmmm, the Almighty is likely to be 10, so that rules out that number, and I thought considering the strength of the evidence, 5 would be the most relevant number. (Biochrome is a science where not much is known, so something definite and unchanging like the heightening that Returned come back at was a good choice). It is possible for there to be more than 10 heightenings, and 4 biochromatic entities. Unlikely, but as we've seen with Allomancy, people generally underestimate a magic system.
Another constant in Awakening would be the number of focuses, Breath, Color and Command, so that would be three.