Development cost depends on various factors such as, availability of developers of the given domain, size of the project, number of technologies to be used (i.e if more than one, is there need to get a developer for each technology or one developer with knowledge of all can handle the job).
This days there has been a call for everyone to know how to code, with tech celebrities and entrepreneurs supporting the project "Code a day" (code.org) and schools introducing programming at elementary level. Even though not everyone will want to follow this path as a career, there will be a huge amount of hubby developers. If this is the case, everyone will probably develop his or her own software, that really doesn't seem practical but with availability of open source tools out there for anyone to fork, build and use, anything could happen.
So what happens when 80% of the population knows how to code, and each person either freelance to get extra cash or works as a full time professional. With this much developers, probably a lot of people will be competing for one job, this means that people can bid for a job, and everyone will like to make his or her price as low as possible in order to get the job, which will probably affect the amount it takes to develop a particular kind of product.
As it is right now in sites like freelancer.com, odesk.com e.t.c, the bids to develop a particular program are so low i am beginning to think how much it will be when we have more developers. But ironically we need more developers, a lot of countries outsource their development jobs to countries like india, and china where professionals do a work for less price, and some countries outsource because there are no good developers to get the job done where they are.
This is just a personal evaluation as i can't predict the future, and i know many of you are thinking about the same thing. Give me your feedback on what you think will happen to development in the future.