The final episode of Big Time Rush is airing this week, and not too many of the cast members seem to be up for any new roles as far as I know. Ciara Bravo finished taping the Nickelodeon made-for-TV movie "Swindle" last year with Jennette McCurdy, Ariana Grande, Noah Munck, and others, and recently she was found to be involved in another that's scheduled for next year.
http://www.justjaredjr.com/2013/06/20/ciara-bravo-jinxed-filming-in-vancouver/

Erin Sanders is still trying to get herself as much exposure as she can:
http://forum.ns4w.org/showthread.php?463784-Erin-Sanders-Annex-Magazine-July-2013

Not sure about anyone else, though.

i'm amazed at how many of Nick's top shows they are cancelling with absolutely no go shows to replace them, it just doesn't make any sense.

Sam & Cat and Wendell & Vinnie are OK, but they aren't nearly as good as the shows they replaced...

I thought the show was going through 2015? Nick is so stupid for getting rid of their best shows!:mad:

Big Time Rush band is on hiatus as of March 2014.

Carlos Pena Jr. last year hosted Nickelodeon's new game show Webheads. The filming of Webheads completed 40 episodes, and as of now Nick hasn't aired Webheads since last year July. 18 remaining episodes have left to air.
And also Carlos Pena Jr. will guest star in upcoming Thundermans episode.

Kendall Schmidt is working on solo music.

James Maslow was on a new Crackle original series, "Sequestered" started in Aug 2014-Oct 2014 with 12 episodes that aired. In March 2014 he competed in season 18 Dancing with the Stars.

Logan Henderson - nothing else is known after Big Time Rush ended.