SO I have no idea if I should start a new thread about this, but according to Darren Robinson the guitarist and back up singer of Phantom Planet who is currently on an indefinite hiatus, Dallon Brobeck will be filling on bass for some of Panic! At The Disco's shows.
Darren Robinson's Twitter
My friend @DallonBrobeck is filling in on bass for PATD for some upcoming shows! Go support them! (PS. Dallon is a total stud, ladies.)
LINKS
____Status Twitter
____Dallon Brobeck's Twitter
I don't know if its true, because it has neither been confirmed nor denied by either Brendon, Spencer or the Panic! At The Disco's web-site soo..
EDIT!
So it appears that Dallon Brobeck is actually Dallon Weekes and that Brobecks is actually a band of his. you can see them here && also, PATDONLINE has also said something about it, the post you can find here