Just... what the hell. Seriously.
So many anime/manga series have ended and people still love them.. it seems ridiculous to me to say that you can't cosplay from a series just because it has finished or it will end soon. It makes no sense either because everything will end someday, even those series that are currently ongoing and have been so for years. It would be like killing the hobby althogether because no series will last forever. Heck, and variation is gold. I like to see both new and older series cosplayed.
*~Cosplays in progress~*
Masamune Date - Sengoku Basara
Eren Yeager (casual outfit) - Attack on Titan
Sanosuke Harada - Hakuōki: Shinsengumi Kitan