let me break it down by parks:
hollywood studios is obviously having the most changes right now. toy story land should be open by the time of your trip, and they're also working on refurbing the one man's dream museum into walt disney presents, which is a combination of a museum and a preview center. there's also a new land, grand avenue, that's usurping the current muppets courtyard and should be open before 2018 starts. they also added projection shows on the chinese theater (disney movie magic and star wars fireworks). the great movie ride closed on august 13 to be replaced with mickey & minnie's runaway railway in 2019, so it won't be open--star wars land is also aiming for 2019.
epcot is next up in line, and while it hasn't had too much work done yet, it's still getting quite a few changes. mission SPACE just reopened with a refurbished queue, new ride film, and a different green team less intense experience that has a lower height requirement. i think you've probably seen the new soarin' film since that opened in june 2016, but if not, you might want to check that out... same with frozen ever after and the new norway section of the world showcase. the universe of energy closed on august 13 (same day as the great movie ride) and they're aiming for a new guardians of the galaxy roller coaster to be opened in 2021. there will be some general construction going on with the addition of a new section in france and a new gondola system to connect the parks with the hotels, so be aware of that.
obviously animal kingdom has pandora which you already know about, but they've extended the hours to add more night time entertainment--a new projection show on the tree of life, safaris at night, and a new water show called rivers of light in asia. work there is basically done for now, though it's rumored there'll be a renovation of the dinosaur section. probably won't be worked on while you're there though
and magic kingdom is having a bit of work done too, but most of it is aiming for the 50th anniversary so not a lot of it will be going on during your trip. the hall of presidents' refurb has been delayed, but it should probably be open by the time you get there--they've added a show with the muppets outside, too. splash mountain will be closed for refurb for about 4 months starting august 28th 2018, so if you're going before then, be sure to get a ride in. main street USA is getting work done, so some buildings will be under scrims, and a new theatre is planned for 2021. they also let people into main street an hour or so before the park officially opens, so the welcome show is at the castle now. the biggest change is that they debuted a new night time show, happily ever after--it's quite a spectacle, so catch it if you can
in terms of other parts of the world, typhoon lagoon got a new ride (miss adventure falls) and disney springs has gotten plenty of dining and shopping in the past two years--most of their focus has been here. there's been miscellaneous work at some of the resorts and complexes, including the previously-mentioned gondola system that's set to open in 2019. if you like personal transportation, they've also begun their own uber-like service called minnie vans. the poly has basically stayed the same since its last refurb in 2015, i think. besides that... i think that should cover most of the major things
