I can see recent Windows Phone purchasers being upset by not having access to WP8.
That said, I think it is more important for Microsoft to move forward with the best technology they can. They'll need all the features announced today if they want to compete successfully with iOS and Android.
If you're the sort of person who doesn't like having your hardware orphaned the same year it's released: don't buy WP7.5 and don't buy Android (which usually ships with out of date software if it's not a Nexus device). This is where iOS should get the credit that it is due. Of course, like iPad 1 users are discussing in another thread, Apple iDevices typically don't stay current for more than 24 months. This isn't a good market to be in if you want to buy a device that will last for 3 years and run the current software that is available.