I've noticed that there has been a lot of confusion in regards to Apple releasing Swift 2 as an open source language. I just wanted to clear a few things up.
1. You still won't be able to develop iOS applications on Windows unless you purchase a Mac.
~Exception: If you are someone who doesn't mind doing it the "hard way" or someone who simply wants to practice writing Swift, you could write native Swift applications, though without the Cocoa framework the work you have to do would most probably be quadrupled. Even then, you wouldn't be able to release your app.
2. You will be able to write Swift applications in Microsoft's new version of Visual Studio, but this doesn't mean you can write apps for iOS or OS X.
Solution: The only solution I recommend is to actually buy a Mac, I know it isn't the most easiest solution for some, but they are offered at a much lower price on trading sites like eBay. You DO NOT require the latest Mac to write apps for iOS, I would say any Mac released 2007+ is suitable.
Reassurance: Most people think buying a $2,999 Mac is what you must do, it isn't true! if you buy a second hand one that isn't too old you'll be just fine!