No. If a majority of employees vote to unionize, by law, the business must recognize the union. In any case, neither 47 nor 49 would do anything to prohibit the formation of unions.
If somebody works somewhere that is unionized but does not want to join the union and be required to pay dues, well that's just too bad in some states. 47 will just make it so that the union can't require you to join as a condition of your employment. Personally, I don't see how it is a bad thing to let people choose, especially since you have no control over how your money is spent. The majority of that money goes to political contributions, and while some people don't mind, others do. This is a good, middle of the road policy that doesn't require union membership, nor does it outlaw unions, it allows the individual to decide.
49 prohibits government from collecting union dues. The Rocky Mountain News endorsed it, and they give a decent rundown of both sides here: http://www.rockymountainnews.com/news/2008/sep/18/yes-on-49/
Hope this helps.
