The biggest threat to moving to Linux...
...has nothing to do with Office 2013 or any office version. It's games (If we are talking home use). For example...if STEAM continues to port games to the linux platform, your gammers, who focus on the latest and greatest coputer hardware and will continue to have full blown computers will, in my opinion, switch to Linux. Beter stability, better performance...and in the future, games...
Businesses are not going to fllock to Linux. Change in the business world is difficult and slow.