The development team works in a way that allows them to focus on developing various projects at once while still being efficient.

A big portion of the castle update is the greatly improved graphics, something that would have been worked on by a graphics artist who really wouldn't have been needed for the new guild system development.

If we look at some of the recently added things that would require scripting such as accessories, who's to say this won't play a part in the new guild system? Maybe it's a potential reward, and if not, there are a couple developers who are capable of producing something like accessories on their own, which allows other developers to work on the new guild system.

The new bounty system is something that appeals to a larger audience than those just interested in guilds and adds more dynamic game play overall, I don't see an issue with this having been worked on alongside the new guild system since they have to focus on the server as a whole which includes accessories as that appeals to a larger audience as well.

The warp ring will be extremely useful come the new guild system as well, and it's really good they added it.

I don't really think it's fair to say they just dropped the new guild system for this because it's not like they stopped working on it all together just for this, they have several developers and they know how to use them best there's no sense in wasting all your developers on one project when you could better use them on other things.