Nah its not next route of Kakumei for sure, they already announced the kakumei series and he said its something "new" but wont answer any questions about it until middle of 2018 (except not being sengoku koihime). Maybe a new koihime series about a different time with different heroines, maybe some other genres like classic moege etc as you've said, we will see.
About the all ages thing, to be honest I'm not sure. Yeah that voice thing was pretty annoying but I dont think it affected sales at all. Actually both of all ages and X version's sales were nice imo (at least from what I can see from tech-gian eroge sales ranking), and its not like Sengoku Koihime X was a remake or something, it was just an extended edition so imo we have to add those two games' sales and count as one, but apparently that wasnt good enough for a 60+ voiced heroines game. Now we will see how much Kakumei sell, I'll be sure to compare those two and will inform at this thread as well.
I'm still very shocked tho. I mean they've made a fandisc even for the Appare Tenka gomen, which made them almost go bankrupt, so I thought we would get one for SK too for sure since thanks to it they somehow regained their core fans.