It's not quite the eve of update, but Windows Phone 7 users should take solace in knowing 7.5 "Mango" will start rolling out "in the next week or two." The announcement comes straight from Microsoft, who also added that it'd be updating the "Where's my phone update?" page at that time to give a better idea of the exact dates. The official Windows Phone Blog cautions against installing unofficial or leaked firmware, of course, so venture down that path at your own risk. As for which device will be the first to join the fun, well, stay tuned.
Source: Windows Phone Blog