iOS 7, 8, or only 9? I haven't seen a mention of this.
What platforms can we target with Swift 2.0?
I would assume the same as Swift 1.x, don't see any reason for that to change. That's just my educated guess though
That is a reasonable assumption but I would NOT make a decision now to use Swift 2 if supporting previous platforms is critical for your app until there is official confirmation of this and Xcode 7 gets all the SDKs and simulators.
There was no official response to an earlier query on this. This should be easy enough for the team to confirm to make it easy and safe for developers to make their migration decisions but they have a habit (conscious or not) of making it unnecessarily difficult in the past. :-)
Note that there was no obvious or language technical reason for dynamic libraries to not be supported in iOS 7, it was a deployment issue. So even if you get your Xcode 7 compiled app to run on previous versions in development environment, there is no guarantee you will be allowed to deploy it.
I can think of several POTENTIAL reasons that previous iOS may not be supported.
1. Lack of sufficient resources to test and certify Swift 2 runtime on previous versions to be confident of allowing it.
2. Dependence on certain changes in underlying SDKs for Swift 2 runtime to work as it stands that may have happened only in iOS 9
Not saying the above is the case. Just saying your assumption is reasonable but not a safe one to make to act on. Each developer should make their own decisions based on the risks that it may not be supported unless officially confirmed.
Based on the videos and some of the new Swift API's are explicitly available on iOS 7 (like #available and guard statements), I'd say Swift 2 will run on iOS 7 and later. The next question is going to be when can we start submitting Swift 2 Apps to the App store. I'm not going to make the change to 2.0 until I know I'll still be able to submit our Apps (or at least have a reasonable accurate timeframe of when I will). And I'll say I really want to make the change to 2.0 ASAP.
Andrew
Edit: The Swift session currently streaming live is making many references to running on iOS 7 and later.