Steve Jobs did product conception. He was not the developer of the ipod. You need not fear. His company will go on without him, although I would not buy stock. Without his product conception and cut-throat business practices, the stock is not likely to increase.
After Steve Jobs died, the developers continued doing their work. He was a CEO, to mean that all he did was to initiate a product, and then developers would continue doing the updates. You need not to worry, updates will definitely continue.