Originally Posted by Fat Mario With Lasers
I suck 200%. If, in the first scenario, we already have 104 standalones and want to get to 77, then the legendaries add up to 116, instead of decreasing it to 92. This means that we'd need at least 39 new evolutions instead of 15. That is, of course, if they add 0 new standalones besides the legendaries. Obviously, that won't happen.
But we'll not be getting a perfect 10% number in Gen VI either; we've never had that number anyway, why would we now? I could see them decreasing it to 13% at best, which would give us a net gain of ~15 evolutons. Much more believable, in my opinion.
What's most likely, however (besides Rowan being WRONG...) is that they'll follow the rough 9% count we have without legendaries; if they want to keep that number, then... we'd need a net gain of ~10 new evos. I don't *like* that number because this is an even Generation and we know they love to evolve old pokémon in those, so I'd bet on the ~15 evos calcs... but I'd be fine with only 10. As long as they evolve the right pokémon (BANETTE) and such.
I don't think 2 generations is enough of a pattern to go off of. It might just be a coincidence or wishful thinking that Gen2 and Gen4 added Evos/Prevos. Gen3 added 2 Prevos, keep in mind.
I'm not saying you're wrong (in fact, I'd like for you to be right), but I think that there's not enough evidence to make a claim such as "every even generation will add new evolutions". But that's just my opinion, so take that as you will.