Unfortunately. Not a single smartphone out there now will be able to upgrade to Windows Phone 8. Which makes it even more frustrating if you're a recent customer. Microsoft is doing with Windows Phone 8, what it has to do: laying the cement for an Os that will last deep into the future.
It's also a fundamental shift, where Microsoft is uprooting everything, and packing up house and putting it back on a truck and moving it out. WP8 will share common code with the impending desktop and tablet versions of Windows 8 and by next year, every new Windows computer, and phone and will have the same modern software DNA.
It's almost like a do-over for them. Which is a good thing. Because now there will be more control from here on out.
There's a lot to look forward to in WP8. 720p hi screens, NFC, Metro UI. Because of Microsoft's iron grip this will keep the platform out of the horrible mess Android has gotten itself in because it's so fragmented now. The way WP7 owners are getting screwed, is a way of getting saved.
A radical cutoff mark means no dizzying fragmentation, but rather a clean break from WP's past and a running start into what's fast, bright, and next.
So here's a piece of advice. Don't buy a Windows Phone until Windows Phone 8 comes out.