As long as new technology emerges, new opportunities will emerge with it. There's also reason to believe that technological change is accelerating, leading to ever more possible great ideas.
Your 'perhaps in a decade or so there will be no more great ideas' reminds me of many failed predictions about the saturation of technology.
Internet, as of today, is a gold rush. Anyone worth his programming skill can work on an idea and get funded. But then, with the passing of time, all the low hanging fruits will be gone. Once we reach that point, good ideas will become scarce. Great ideas may not even emerge. VC funding will be gone too. Perhaps, in a decade or so.
Internet based companies are extremely easy to replace today. A chilling fact but true. Compare this with firms like Citibank, British Petroleum, etc. They have been here for decades and will be here. The same cannot be said for companies like Facebook and to a large extent Apple.