Looking at your list of vacations in your signature block, looks like to haven't been since Summer 2011. There are several new things to see since that time even if you are waiting for Star Wars Land and Toy Story Land to complete. The list includes, but not limited to:
- New Fantasyland (ex: Seven Dwarfs Mine Ride)
- New Soarin'
- Frozen Ever After
- Happily Ever After fireworks
- Pandora
- Nighttime Animal Kingdom (Rivers of Light show, safari at night, etc.)
Also, the new lands for Hollywood Studios are at least a year away and the first year will be brutal since everyone is going to make this their first priority. If this is a "one and done" type of vacation, I would probably postpone until 2021-2022 during the 50th anniversary since Epcot is getting a lot of attractions as mentioned in
D23 today. However, one thing is that WDW will always be changing with new attractions to keep up with neighboring theme parks. For me, a trip every 2-3 years keeps me interested and new attractions pop up to make it feel like I am never getting bored with WDW. Since 2011 was your last trip, I would try to go either later this year or next year and schedule another trip during the 50th anniversary.