I have it on my old fashioned iPod 4th gen. (it feels like a PC from 2000 in my case compared to the Lumia 920) and it would be great to use the power of the WP camera... Even if they made a 3rd party app for it, I'd be completely okay with it. (day 5 of my WP and I'm in love)
By the way, for all you facebookers looking at this, go to this link here: https://www.facebook.com/snapchat?fref=ts and klick the drop down menu. Hit contact developers and send them a well worded message about it.
Like others have said, the more requests for the app itself, the better chance of the app coming to the WP platform.