Windows Phone is the new Android
If WP8 doesn't get to current devices, that will really remind me of Android, especially Ice Cream Sandwich. Basically, Android phones are almost never upgraded, even the Nexus line is rarely at the exact latest build of Android (4.0.4 is the latest but many Galaxy Nexuses don't have that, not to mention the different Nexus S's, and the Nexus One got hosed for Ice Cream Sandwich).
So I guess here's how it breaks down:
Android's best case upgrade scenario is with the Nexus One; updates from Jan 2010 to the last Gingerbread release, Sep 2011? -> 1 year 8 months maybe?
Windows Phone's history so far: devices released late October early November 2010 will be updated at least through Tango and possibly a moderately WP8-esque release, figure about this summer? Maybe July 2012ish. 1 year, 6 (Tango only)-12 (WP8ish release that isn't really WP8) months maybe.
Worst case scenario for both is that you buy a new phone that's soon outdated or it's even already outdated and you never get upgraded. You might buy a Lumia 900 the day before Apollo comes out and then get hosed for Apollo, or with Android you get hosed with a manufacturer that refuses to update beyond your current device.
Looks like the scenarios are actually pretty similar, though still sucks for any user who gets hosed for updates.
The real winner out of all this looks to be Apple if anything. The iPhone 3GS will probably be updated right up until iOS 6, giving it nearly 3 full years of updates. The worse case scenario with any iPhone so far has been that you get 2 years of updates, that's been the case with the original and 3G iPhones.
Long story short: both Android and possibly Windows Phone throw you to the wolves for updates, Apple has the best track record so far for updates. If updates are getting you down then that's just something you'll have to accept for now.
One final note though, if there is a moderately similar to Apollo release for current phones, then that's the best you could realistically expect, because there's always going to be limits to what features you put into an outdated device. I just hope there isn't too significant fragmentation between WP7 and WP8 if this news turns out to be true.