According to Evans Data Corp, the global developer population will approach 19 million in 2010. (I found this via ZDNet's ITFacts blog; the EDC site requires registration to even see the press release.) That's quite a big number - the total population of Australia, for example.
Programming will not be a marginal activity, and any fundamental cognitive constraints on our ability to develop increasingly complex problems will be impossible to avoid.
A lot of the growth will come from new countries bringing programmers online: EDC forecasts that the developer population in APAC will grow by 83% increase from 2006 to 2010, compared to just a 15% increase in North America for the same period. This will keep the skill level high, since only very talented people will enter the population, rather than expanding the percentage of the programming population - and thus reducing average skill - in a given country.
Therefore, the qualititative problems of programming won't change much in the next 5-10 years. However, beyond that we may also face the issue of reducing innate skill levels of programmers.