Microsoft said that they will have ARM based tablets (running Windows RT) with Office 2013, including Word, Excel, PowerPoint, and OneNote. Also note that, if you like Outlook, you will still have to pay to use it on the tablet.
Now you may be thinking: “Why would Microsoft, who’s asking more money just for Service Packs, give what otherwise costs hundreds of dollars (through them) for free? Are they suddenly feeling like they don’t want to rip people off too much?”
And you would have a good point. But Microsoft is betting on the ARM-based system (which, as you may recall, is optimized only for the tablet) to become more popular. So they are offering Office 2013 (which could technically be replaced by Libre Office or Open Office and the like) to woo customers into tablets – not to mention repulsing them out of the laptop/desktop market through the UI.
However, it would seem that the competitors, up to now, are only compiled for the x86 platform, and would give Microsoft an advantage even if they didn’t offer it free.
However, before you run off to pre-order one of these, just remember that, unless you have a keyboard, typing will be a real pain in the neck.