Reports from all over the Twitter-verse are that Castle has gotten a full season pickup at ABC.
Given its ratings stability (and actually up a tick last night) and especially how well it has performed versus the Tuesday and Wednesday freshman shows at 10pm, The Forgotten and Eastwick, it's not particularly surprising.
Either way we'll have Castle around all season to figure out its renewal prospects for next season.
I wouldn't see this as necessarily bad news for The Forgotten and Eastwick -- that bad news for those shows are the numbers, which are very bad indeed. Castle smells like a rose by comparison.