So, what does this mean for developers? Is Salesforce switching off the old UI? No… well not yet, too many companies have invested too much in it and VisualForce. Are they switching off Visualforce? will you still be able to develop VisualForce? Yes of course.
The Lightning UI is still a little way off from being complete. One of the reasons is that it doesn’t have a vast amount of components that VisualForce has, but this is defiantly going to change! With Lightning Components your creating a whole application rather than just a page in VisualForce, so the complexity is higher than regular VisualForce. Read more