We've got 12. Current holders include:
Lya -- Aebys, the original pen
Viserys -- for ruling
Dany -- for a pet I guess ¯\_(ツ)_/¯
Ser Richard -- war logistics
Garin -- merchantile stuff
Alinor -- administration of the Realm
Teana -- administering the Scholarum
Tyene -- intrigue and to help keep track of poison crafting
Waymar -- to help with alchemy
Vee -- so she doesn't have to read and write
Xor -- Since he doesn't have arms in his natural form
Maelor -- Just because
1 extra up with Bloodraven right now learning all that extra lore for us. So that's 13 dragonpens in existence.
Anyway, DP has told us that
everyone wants a dragonpen because they're very useful and genuinely love to serve, so since everyone wanted one I'm assuming that everyone truly had a good use for them even if we can't really see it (like Dany getting a pen). Either way, they are fantastic status symbols. Rhaella and Malarys are next in line for their own pens.
But that being said
@das_slash, I'm against just making more pens if we don't have people to take them when they're done copying stuff down. These pens need masters to protect them from theft.
Maybe in the near future we can give pens to Kyla, Leila, Valaena, etc, but that'd be far in the future if they finally reach full PC levels.