Oh yeah as for the mod slow down.
During the 1.8 release, bukkit had the dmca takedown. Something that made it almost impossible to update bukkit.
This lead to many developers, like myself thinking Bukkit was dead and had to move on. Now i was lucky enough to see the rise of Sponge however I know a few people who just left the whole minecraft community.
I believe that some developers followed suit and left before sponge was even heard of. And other developers fear to program on bukkit due to the way they are updating bukkit .... Well its in a grey area. And they don't move to sponge because they either have not heard of it (I am doing my best to make people aware but a few of my bukkit fans dont know that sponge is a thing) or they think its too unstable considering how large minecraft is and the fact sponge has been in development for 2 years (thats quick). And the fact the beta sign on sponge might scare away some developers.
I do believe there will be a time where plugins are developed on a daily basis again, but not for a while as we need people to move to sponge before it can start