I hope there will be option to disable Siri. Don't want turned on mic 24/7.
This means that Apple isn't listening to you 24/7, only when Siri is activated. Sure, sometimes it's activated accidentally and might overhear something you didn't want it to, but those times are pretty rare.
If Apple introduces a "Hey Siri" feature on the Mac (which it's unclear about given the fact that in the demo Craig activated Siri by clicking on the icon, then later by pressing a key on the keyboard), I expect it would operate in the same way.
Finally, I'm sure there's a software setting you can use to disable Siri if you really don't want it to be activated.
what?! your proof that Apple isn't listening 24/7 is not a proof at all. A device that is listening to you 24/7 to hear when you say "hey Siri" can tell you "you can't use it because you are not online" whenever it wants to, and I don't think anybody was suggesting that Apple servers were capable of listening in when you have no network.
Apple has been shown in the past to log information on the device itself, however.
I was pretty disappointed by this WWDC. Any info on next XCode version?
Before you decide you're disappointed, wait for the Developer State of the Union later today and the other sessions. There's interesting things like an "Apple File System" session. It looks like the beta for the file system will be in macOS Sierra and come out officially in 2017. You won't be able to use it as a boot drive (probably a safe precaution) and it has a few other restrictions, but it's a good start.