There's a small but noticeable difference in field of view between the 16mm and 18mm Fuji lenses. Whether that translates into something useful for your photography is, of course, not something we can answer. Your current lens is a zoom, so it's more versatile. It has OIS. It's a great little lens overall. The new Fuji 16/2.8 is likely to be slightly sharper -- though probably not noticeable in prints. It's certainly smaller and lighter, and "weather sealed" whatever that means. It's fairly inexpensive at US$400. I'm very likely to get one, as I have a serious GAS problem with the Fuji wide angle primes. And the wide angle zooms. OK, I have a GAS problem with Fuji lenses. Fine.
I think I agree with Paulo and would recommend the 14mm f/2.8. It pairs up very well with the 18-55 zoom. It's significantly wider in field of view, still fairly compact, and incredibly well corrected optically. They are not that expensive on the used market.
For me, the new 16mm f/2.8 is a lens I would pair up with one of the 35mm lenses and the 50mm f/2 as a small, light, 3-lens prime kit. I probably wouldn't carry the 16 and the 18-55, I would just take the 18-55 by itself for maximum simplicity.