Anyone who does in-depth statistical analysis can use R. It is equivalent to SPSS, SAS, and matlab in its applicability, plus its free.
People involved in 'big data' and serious analytics in business are already using R a lot of the time. The other group of people in business who use the closed source applications above, however, aren't as technical, and have a pretty big roadblock ahead of them.
The issue is just a question about ease of use. There are companies out there who offer products that compare with the above (http://www.revolutionanalytics.com/), but they still cost money. The 'problem' of R in business is that there aren't any good GUI's for it that allow you to just go menu>ANOVA>3 way factorial>[settings dialog]>Calculate and then get there.
Of course there are a few other reasons why those other applications exist and thrive in spite of R, but I think the limited use cases and lack of a comprehensive GUI are its biggest roadblocks.