If I see the current usage of different operating systems, there is scope of Linux OS in next 2-3 years to expand from its present user base of 5%. Simply put, significant volume of users are still using Windows XP even after the support for it has ended. Currently the app providers are supporting XP but within 2 years or so that support would be minimal. Further, a significant chunk of that XP user base have desktops on which the latest Windows7 or Windows8 would not load.
That gives an opportunity for a linux OS to fulfill the gap which would run smoothly on the antiquated hardware and provide full functionality to the users. The OSs with similar kind of potential I see are Lubuntu and Xubuntu. Clearly Ubuntu is directly competing with Windows and Mac in terms of looks and functionality and I don't think future Ubuntu releases will load smoothly on these machines running XP. Lubuntu and Xubuntu can fill the gap. From functional point of view, both of these distributions are competent to challenge any modern OS in the linux world. They have all the apps you would require normally and of course, there is WINE to support the Windows apps one would like to use.
Another significant OS which looks and feels like Windows 7 and can bridge the gap, is Zorin OS. I was unable to boot it from an USB but really interested to try it for sometime. It has definitely great potential but unlike regular linux distros, the full version is not free. Unfortunate.
Some of my next few articles would concentrate on the operating systems which look and feel like Windows XP and potentially can cater the segment who can't or don't want to migrate to Windows 7.