Doesn't seem like there are any waterproof cases for the 4, so I doubt we will see any for the 5. Maybe more likely now that the phone is available in the US at least. Not a fan of the waterproof bag idea myself.
At least my tank bag has the option for a waterproof cell phone pocket though, I doubt the touch screen would work through the thick plastic. Never tried it because I don't have the pouch required to keep the phone in place on the bag.
That's not what I mean when I talk about a case, I mean something I can keep on all of the time. Something like an otterbox fre would be more appropriate. Or the old lifeproof cases like I had for my iPhone 4S. I live in a climate where it is pretty much always raining. My Pixel 3 can get drenched to the point you cant even use the touch screen anymore with no issues. Plus it can mount straight to my handlebars with a quadlock case instead of having to put on my tank bag and strap it to that.
Well, IPx5 is technically water resistant for water jets and up to 12.5 liters per minute. I think that sounds enough to be used it rain. I also saw some reviews of other devices that even IPx4 is fine in rain.