If they do tiers, then clearly both Pandora rides will be in tier 1. I would guess RoL would be in 2 (see below). Everything else will be in 2 also. You can only pick one tier 1 in advance, and so there has to be enough tier 2s for everyone to get their 3 in advance. If they put too much in tier 1, everyone would get a tier 1, but tier 2 would run out.
If tier 1 runs out (which it most likely will), people could still pick three tier 2s.
So, what about RoL?
Both Pandora rides will run out pretty quickly, even with both in tier 1. Having RoL in tier 1 would then result in pushing people to take it once Pandora rides are gone (the psychological push of needing to take their tier 1). This would result in RoL being gone even sooner.
By leaving RoL in tier 2, it would result in more people picking other attractions and utilizing other means (dining package or stand by) for RoL. Remember, if people take a Pandora ride and RoL, then they are left with only one other FP for the entire day! Not an attractive option.
Now, having the tier 1s run out so quickly (as would be the case with only 2 rides in the category) would be bad optics.
So, I predict they won't call it tiers.
They will say, "Animal Kingdom is not moving to a tiered fast pass system. However, you will not be able to select both of the Pandora rides in your initial set of 3 fast passes."