If the latest rumor is to be believed, Microsoft is apparently having a "meaningful look" into producing a full native port of Office to Linux, with 2014 being a possible launch year. Open source veteran Michael Larabel heard from a source at the Free and Open source Software Developers' European Meeting (FOSDEM) about Microsoft's plans, with reason being that Linux is "showing signs of commercial viability on the desktop."
Speculation is that Office for Android will serve as a stepping stone for Office on Linux desktop computers, as porting a portion of the software for Google's Linux-based OS will make it a lot easier to bring the full software to Linux. Microsoft already has experience with Linux; they have a department that specializes in maintaining Hyper-V virtualization compatibility, as well as a version of Skype for Linux.
Larabel will not be surprised if there are "many doubters" for plans to bring Office to Linux, as it seems like an unlikely target for Microsoft to spend resources on considering the low market share of Linux. However, the guy was right about Valve bringing Steam to Linux, so it remains to be seen if Office will be seen on the platform.