Microsoft CEO Steve Ballmer is set to take to the stage in San Francisco at 8pm (GMT) tonight to announce the company’s next big reveal. While we have it on good authority that we’ll be seeing the new Office 15 productivity suite, what features this will entail remains a mystery.

Among the main beneficiaries of Office 15 look set to be tablet users, with an optimised mode for touch devices. In light of Microsoft unveiling its two Surface tablet devices in the shape of the Surface for Windows RT and Surface for Windows 8 Pro this appears a logical move. 

However, users who may miss out on the joys of Office 15 appear likely to be those who have PCs that run Windows XP and Windows Vista. Reports suggest the suite will only be compatible with Windows versions 7 and 8 and Microsoft has spoken in the past about moving away from these older operating systems, particularly Windows XP.

The introduction of Office 15 could coincide with a new Office Marketplace that will enable users to purchase specific tools and extensions to support specific needs. It’s also expected that Ballmer will reveal deeper cloud integration for the likes of Facebook, Flickr and Hotmail.

Something that divided opinion in previous versions of Office was the Ribbon UI. Microsoft is rumoured to have removed it from the foreground opting for a cleaner more back to basics look.

If Office 12 does indeed have an optimised mode for tablets, could Microsoft finally be about to make its Office Suite available to other operating systems? Having previously remained adamant that it would not be making its suite available to rival companies, Microsoft is thought to be softening its stance. Might Ballmer announce Office 12's availability on both the iPad and Android tablet devices?

All will be revealed later this evening and of course Pocket-lint will be on point to bring you all the latest news.

What do you think Office 15 will bring? Let us know in the comments below.