Sell NX500 for Fuji X-T20? Keep NX1?

...because:

1.  To begin with, Fuji is a really wonderful brand of camera.  Fuji users tend to be very, very loyal (some being fanatic).  The brand tends to grow on you (well, for most it does) and there are quite a few Fuji users who are either still using some Samsung NX cameras, or who have previously used them.  I've been shooting with Fuji X series cameras - both their X-Trans models and their Bayer X-A series - for over 6 years now and I've enjoyed them ever since.  Fuji has a rich color tonality and they are more competent rendering cleaner high ISO scenarios.

2.  OK - for me - this "which NX camera to sell" is quite easy.  The NX1 is a masterpiece.  Yes, it is a heavier and larger model, but it will still remain relevant a decade from now (I believe), so I would NOT sell that one.  The NX500 is a nice camera also, but IMO, I'd sell it with the lenses you described.  This way you'd still have your foot in the door with the state of the art NX1 and S lenses.  So let the NX500 be the sacrificial lamb in this regard and begin enjoying the Fuji X-T20.  You'd experienced more seller's remorse if you let go of your NX1.  This is a "no brainer" in my opinion.

3.  On the other hand, another option is to keep all of your NX gear and see if you can somehow manage to obtain the X-T20 and lens also.  I say this because it's nice to be able to shoot with more than one brand.  It certainly adds flexibility.   There are many dual (and more) system users who post here (and other brand forums).  But it is understandable if it is a "must" that you first sell off a few items in order to be able to afford the next toy.