Here’s a great blog post by Julia White, General Manager for the Office Product Management team.
In particular, her discussion of Universal Apps sounds promising:
“Office “universal” apps on Windows 10 deliver a touch and mobile-first experience across devices
Office for Windows 10 offers touch-optimized versions of Word, Excel, PowerPoint, OneNote and Outlook that work great on small screen devices like your phone and tablet—all the way up to the Microsoft Surface Hub. They are designed from the ground up to run on Windows 10, built for touch and offer the unmistakable Office experience you know and love. As “universal” Office apps, they truly are the same app across device size, providing a consistent way for independent software vendors and developers to extend and integrate with Office apps.
These new Office apps will be pre-installed for free on phones and small tablets running Windows 10, and available to download from the Windows Store for other devices. The Office universal apps will be available with the Windows 10 Technical Preview in the coming weeks and general availability is on track for later this year.”