Opportunities in open source will, to a large extent, be in **Support**. Support for installation and maintenance of OSs and stand-alone and web-based applications. More importantly, like @Mitte says, support for Server and Network installation, administration and maintenance.
I see a time when open source will be used, not only by the technically inclined, but also seriously evaluated based on customer requirements.
@Sandeep, if you can get skilled in developing web-based software and offer this as a SaaS (Software-as-Service; pay-per-use) model, the revenue will come. As long as, like any other product or service, it serves customers well.
And, of course, training!