Specifically, how often are WvW guilds interested in training or marshalling more players into WvW? For some time now WvW chats have stated that they've lost lots of players. Sometimes when I look at team chat I'm reminded that some of it is server-hopping.
Is there any desire or initiative to recruit from outside? One would assume that this is how it's done in some way, but I find that there are a lot of players who take a "revolving door" approach and hop servers to join guilds and play that way. Ignoring the implications of alliances since they are not live at the time of this post, the "jump ship" bandwagon appears to be how most WvW guilds acquire new members.
Very few people would say PvE has a small population, and I would suggest perhaps looking there for new people. Why? I recently added some members to my guild who were completely disillusioned with any competitive formats. Slowly over the last several months I have managed to get them to tag along with a group of us and they've since expressed their increasing appreciation for the game mode and the guild as well. I am often reminded by them that if it weren't for the group of people they play with, they would probably not have given the game mode a shot. So coming back full-circle, I wonder why it doesn't appear that people want to try to recruit from outside since that's where all the manpower is.
Potential requires action in order to be realized.