The title for 6x01 dropped today, so now we have titles for the first 5 episodes:

6x01 Valkyrie
6x02 Better Half
6x03 Need to Know
6x04 Number One Fan
6x05 Time Will Tell

Also, Andrew Marlowe gave Marisa Roffman what I think may be the least spoilery interview ever:

CASTLE: Andrew Marlowe Teases the Castle and Beckett Dynamic in Season 6