Are motivational theorists still relevant?

To motivate employee is very important to a company. Because of the recession the unemployment is increasing. Many companies cut jobs to reduce costs. So how to motivate employees and increase productivity is very important. So I think motivational theorists are still very useful and it’s necessary to learn it. There are many famous theorists such as Taylor Hertzberg, Mayo, Maslow, Vroom and McGregor. In different situation we should use different way to motivate people. For example, after you cut many jobs in company, employees will under pressure and afraid to loss job(Hertzberg demotivate - pressure). If some people work for money, pay more money is a good way to motivate them(Taylor payment buy results).
In a word, motivational theorists are still useful and helpful for management. The point is if we can use it correctly.