Six Sigma is a business success philosophy in some companies, but a flavour of the month programme in others. It is integrated into the problem solving approaches of the company in certain cases with great success, but in most cases, organizations and management practices may not sufficiently to use data to drive decision making (which is what Six Sigma is about, at many levels). That said, Six Sigma training/skills may be exactly what some of these organizations require.
Getting trained in the Six Sigma tool set is now easier than it was, with a number of organizations offering training programmes that meet RABQSA requirements. Additionally, companies like GE, Motorola, Caterpillar and others have well developed internal training programmes that develop the ability of managers to use the tools and methods in the Six Sigma tool set in projects.
The value of Six Sigma certification is not limited to large organizations. In
consulting firms, one needs to address the needs of diverse companies, and that makes a certification in Six Sigma tools and methods valuable. In manufacturing facilities small and large that deal with moderate or large production volumes, the methods used in Six Sigma come into play. A lot of the cost of designs are built into them, and using approaches like the Taguchi method can improve the costs associated with sub-optimal design. These are also part of the spectrum of Six Sigma tools and methods.
Ultimately, it is important to understand what Six Sigma gives you - the ability to look at data and interpret it analytically or statistically being just one of them, and besides this, skills in process mapping/representation, risk management methods, studying the capability of processes, setting benchmarks within organizations, and more. These skills may be called by other names in other industries, but will continue to be important in future.