When you talk about BrokenLens 'dying', you have to take into consideration that perhaps Minecraft itself is dying, too. Minecraft has been around for a very long time— a whole decade of exploration, adventure, and fun. However, there is only so much you can do, and at some point people will end up losing interest. That's not to say Minecraft isn't popular; obviously there is still a lot of interest in Minecraft, but overall it simply isn't as big as it used to be. And, well, that will of course affect the number of players playing at any given time.
I don't think BrokenLens is dying just because of a lack of content. Sure, it could be a reason some people leave, but overall I think it's dying as a result of Minecraft itself dying out.
Aside from that, I don't think there's a need for any more staff. Things can be a little slow at times but things are getting done, and it will only be a very minor convenience to have more. Of course, it would be nice to have another dev— just someone to lend Vertx a helping hand in debugging, fixing issues and coding. However I doubt it's easy to find someone who will do it for free, especially considering it is a very difficult and complex job which requires a specific skill set. So for now, I think we will be fine.