Many (most) interesting sets that go OoP see their prices raising, indeed, especially when they're new.
There's no absolute rule, but at least the UCS sets (the most expensive ones) usually don't go down on price.
The most shining example is the UCS Falcon. Used to be ~$450 new, now it's typically $3000 even used...
Not all sets raise this way, but I'm pretty sure that all UCS sets, at least, should worth more now used than new when they were sold.
Used Lambda Shuttle is over $500, SSD is $800+, same for Blockade runner, Y-Wing, Snowspeeder, ISD and Death Star are $1000+...
You still have to find a buyer, but yes, prices usually increase. There's in fact forums of investors specialized in Lego investments ^_^
One (75054) has been released in 2014 and discontinued a couple of months back, so probably not soon, but you never know. Maybe with Rogue One.
It's actually a good example of price:
- it was sold for a bit more than $100
- now it's discontinued, you'll find it for more than $200 new from 3rd-party sellers on Amazon or other stores (probably Ebay, too)
- price on Bricklink (the Ebay for Lego) is ~$150 for new ones... there's not many used ones, but it's probably already more expensive used now than new when it was available.