SideKick will not be without its operating system which was probably the most delightful mobile OS to use before the iPhone. SideKick phones has probably not been selling at the same brisk pace it enjoyed prior the iPhone's release. Everyone knows there's a new "It" phone in town and it's operating exclusively via AT&T.
Microsoft, as the new owner of Danger, is perhaps a logical choice. It's Apple's biggest rival and thus has a lot lose if Apple continues increasing its mobile market share. For SideKick fans, the good news is, Danger will remain intact, but more will be required of the team as Microsoft contemplates its future in the mobile industry (some of the team will join the Premium Mobile Experiences Group at Microsoft).
Britt and Hersenson, founders of Danger, likes the setup: "As we combine our team and technologies with Microsoft, we see a clear path to evolving that experience and delivering it to an even broader group of consumers."