Although it won't arrive this week, as previously rumored, Windows Phone 7.5 Mango is really close to becoming available to older WP handsets.
Microsoft has announced via the official Windows Phone blog
that Mango updates are expected “to start rolling it out in the next
week or two.” That's certainly good news for those currently owning a
Windows Phone 7 device. All WP7 handsets will get the update, with no exception, although the exact timing will depend on manufacturers and carriers.
source:Unwired View