I just sold my iphone X last night, got a great offer at pretty close to retail. I had gotten a replacement device as i had an overheating problem, and just decided to sell the brand new one they gave me as its easier to sell brand new iphones. I did that because i really want the iphone X+ (Gold), the iphone X is too small for me. Plus the resale value will be at its highest now; once the phones are announced and people are looking to upgrade, the market will be flooded with used iphone X's and not to mention that there will be a newer version of the same phone being released as well.
So now i'll just have to use my old 6s for 6 weeks until the X+ will be in store, which isn't that long at all. To be honest, using the 6s again isn't as bad as i thought. It's a bit slower, screen isn't nearly as good, and the battery drains really fast, but all the other things i need are there.
Unless Apple comes out with something totally different in 2019, i'll be keeping the X+ for 2 years until Sept 2020.