This has been a long wait, not so much because of the way S3 ended but simply because I have enjoyed this show immensely for most of its run so far. To be honest, I don't expect the plots to become any deeper. However, it will be interesting to see who they integrate this new captain into the overall run. From the write up in the link above, I get the impression she's a no-nonsense uncompromising figure. That alone spells trouble for Castle's continuing presence in the precinct.