At Microsoft Windows 10 event the company went over how universal apps would have the the same or a very similar experience across all devices. Office was part of that conversation, and Microsoft just that their next installment of Desktop applications will arrive before the end of 2015.
The update for mobile, labeled Office for Windows 10 will actually come pre-installed on phones and tablets running Windows 10 free of charge. This will include touch-enabled Word, Excel, PowerPoint, OneNote and Outlook. Microsoft says that Office 2016 for desktops will come during the second half of this year. I would expect to see it around the back to school time.
Source: Engadget | News Archive