The book "The Major Transitions in Evolution" fairly cleraly lays out many of the previous major transitions. Evolution has taken multiple major steps forwards before - for example, with the last genetic takeover, or with the origin of sex.
In my view, what we are seeing now is a modern genetic takeover. If so, we do have a useful reference class.
The genetic takeover/substrate migration is a useful reference class, but (although I agree with you that in some weak sense the intelligence explosion is already underway) minds that can rewrite themselves in place will be qualitatively different from anything that has happened before.
If you have graphic design experience, check out the on-going logo design competition at 99designs for the Singularity Institute. There are still 6 days left to enter and be eligible to win the $295 prize if your design is selected. Tell your friends with graphic design experience too. There are very few submissions currently.
Note: This is a blind contest. Designers can only see their own entries. All designs will be revealed when the contest ends.
If you're interested at getting a peek at the designs, they will be online after the competition is over. This is standard practice in 99designs contests to prevent designers from contaminating each other and having all the designs drift in a certain direction.