Samsung graciously upped the Galaxy S8's base storage to 64GB this year, but it's sticking with 4GB of RAM. You want more? Hopefully you live in certain markets like China and South Korea. You might have another option that doesn't require moving across the globe very soon. An unlocked version of this phone is launching soon in Hong Kong, which means it'll probably show up elsewhere via reselling.
Just like the locked versions, this phone will have 128GB of storage and 6GB of RAM. Since it won't be carrier locked, someone could buy the device in Hong Kong and sell it overseas. And you better believe people are going to be doing that. You'll probably pay an exorbitant amount to get one, but it's the only way you'll get a beefier GS8 Plus outside the official markets.
While this phone will work anyplace, the band support might be lacking. Hong Kong and China run on very different bands, and it's unclear if this device will have many of the one we need in other areas of the world. It's launching on may 25th in Hong Kong. I'm sure this phone will end up for sale on the gray market soon after.