There is something to be said about the original X-trans sensor, even in 2018. The X-Pro1, in a lot of people's minds, has sat behind the X-T1. Specs-wise is this very true. The X-T's are released later that the X-Pro's, meaning they always benefit from hardware boosts. However, as much as I used to love my old X-T1, there is something to be said for the X-Pro 1's sensor.
With the latest firmware update, the X-Pro 1 is much more appealing. The autofocus is decent, okay it won't rival the X-T2, it can be used with decent street lenses like the 23mm F2. I think the camera always had a bad rep' for autofocus, which never really bothered me that much, as I tend to manual focus more.
The image quality is fantastic, and has a more unique feel than the latest X-Trans sensors (and that is saying a lot because the X-T2 is a lovely camera).
My only real issue with the camera is that it cannot do silent shutter. This is a must for mirrorless cameras for street photography, and it seems odd that it was not set up to have this feature.
The overriding question is can it hold up in 2018? Yes. Does it matter that it has a 16mp sensor? No. The images are sharp and look fantastic printed large. That is less of an issue for me than not having a silent shutter. So if you have a chance to pick up one cheap, I say: go for it! you can always sell the camera for the same price you got it.