I had no issue at all with IQ on the 18mm f2, nor did I find the focus speed a problem. It also made for a very small combo with the X-T20. However, I decided to go a different route with the XF 18-55 for more versatility. I gave up the compactness, but I just didn't feel like I could justify keeping lenses around I wasn't using.
The current version is not my favourite lens, partly because it's good but not great, partly because there are other lenses - not least the aforementioned 18-55 - which cover the focal length better, and partly because it is a bit of a meh field of view for me. Seldom wide enough and just a bit loose for general use.
So I won't be in the market for a Mk.2 but if I was, faster AF and WR would be a must.
I only have the 18/2 and 35/1.4. I rarely use the 18/2. Not because it is a bad lens, but I am in love with the 35/1.4. It's probably my all time favorite lens in any mirrorless system that I have used. The IQ of the 18 is fine for me. AF is no worse than the 35. But I am not as comfortable using wider than 35mm (in full frame focal length).
I'd rather have 16mm than 18mm, as well, if we're voting. As for the current 18, from what I've seen (I don't own one) it's similar to the 27... good, not great. It suffers mostly by being compared to all the other Fuji XF lenses. I so often opt not to use the 27 for that reason, only going with it when space is at a PREMIUM, at which point I'm glad to have it.
It's small and portable. Its IQ is not in the same league as the 35/1.4 or any of the other X lenses I have used (14/2.8, 18-55, 50/2, 56/1.2, 60/2.4, 90/2, Touit 32/1.8). But I find the IQ perfectly acceptable. AF speed is also on the slow side compared to the newer lenses.
I picked my 18 f2 up used for $200, in great shape. I love it, it stays on one of my X-T1 bodies all the time. I like the close focus distance of 7 inches, makes the lens a lot more versatile. It may not be Fuji's sharpest lens, but it's sharper than my Canon 28mm f2.8, especially in the corners, wide open. I won't be selling mine soon.