Regarding file formats: I may be mistaken, but most of the issues I see are with old formats from the pre-internet era and more primitive/obscure OSes. Sure, we all have read stories of old disks which are now unreadable because the hardware doesn't exist anymore, but that is *hardware*. For files, I see VLC can open nearly every video and audio format in existence, and certainly any photo viewer worth using can open more image formats than what I have seen.
Most of us know what we have in our hard drives. I know I only have a couple word documents that may not be supported in the future, all the rest are open formats, not tied to a single software suite. So, as long as the internet exists, I'll be able to download some linux distro like Slackware (I mention it because it includes everything I may need to open my files in a single dvd, no online repositories needed) and use whatever software comes with it to open my files. I actually keep an ISO handy, so as long as VirtualBox exists I can load the ISO there and have a "2015-compatible" SO for as long as I may want to. Damn, if tomorrow we all leave x86 to some other thing and VirtualBox dissapears, I'll probably be able to open a VM and run VB on it
Cloud stuff is probably a huge headache waiting to happen. I'd make sure I have a copy of anything stored in the cloud, and in a format I can open locally. Still, if tomorrow MS dissapears, I'm 99% sure we will have a chance to download Office 365 files in an open format before the shutdown