Machines designing machines will indeed be a massive change to the way phenotypes evolve. However it is already going on today - to some extent.

I expect machine intelligence won't surpass human intelligence rapidly - but rather gradually, one faculty at a time. Memory and much calculation have already gone.

The extent to which machines design and build other machines has been gradually increasing for decades - in a process known as "automation". That process may pick up speed, and perhaps by the time machines are doing more cognitive work than humans it might be going at a reasonable rate.

Automation takes over jobs gradually - partly because the skills needed for those jobs are not really human-level. Many cleaners and bank tellers were not using their brain to its full capacity in their work - and simple machines could do their jobs for them.

However, this bunches together the remaining human workers somewhat - likely increasing the rate at which their jobs will eventually go.

So: possibly relatively rapid and dramatic changes - but most of the ideas used to justify using the "singularity" term seem wrong. Here is some more orthodox terminology:

http://en.wikipedia.org/wiki/Digital_Revolution

http://en.wikipedia.org/wiki/Information_Revolution

I discussed this terminology in a recent video/essay:

http://alife.co.uk/essays/engineering_revolution/