Should I get Island Living on Sale?

I'd say 30 is pretty much what it's worth. It's a little more than a GP to me, if only for the huge world, the new activities and the many beautiful BB it comes with, making it more akin to a TS3 world pack than a TS4 EP and those used to cost, if I'm not mistaken, around 30 :D So, I would personally say go for it, but then again, I have no regrets about having bought it for 35 so yeah, perspectives. If you really think you would enjoy it, and enjoy TS4 in general, I doubt you'll regret it. If you don't like TS4 much, then honestly, even at 50% off, you might not like what you're getting.

Since you asked I am glad you the OP is going to wait for an 50% sale for that for me is what it is worth to me as it originally was thought out to be an GP.