If your phone is running Windows Phone 7, you'll be able to upgrade to Windows Phone 8 when it comes out. Yes, even if your handset was among the first to market. Hey Android, are you listening? That's how you do upgrades.
Update: The Verge is reporting that the upgrade path might not be quite as straightforward as suggested.
The announcement was made by a Microsoft spokesman earlier today and was pretty explicit:
Q: In terms of devices, who today have one is it expectable that…
A: What Microsoft said/stated and what I'm allowed to tell you is that all actual devices will get upgrade to the next major version of Windows Phone (we´re talking about Apollo)
This means that the Windows Phone upgrade schedule is going to resemble the iOS upgrade schedule, with all devices getting upgrades at the same time. It prevents fragmentation and keeps early adopters happy. Good on you, Windows Phone! Now you just need to get your shit together, and we'll be in good shape. [WMPowerUser via TheNextWeb]