OK, folks.  I used a pencil and a ruler to extrapolate the curve to make a guess at the date of the next release event.  I'll call it Slackware 15.1, but it may be something else.  I'm just predicting the next event, not the name of the event.

So I got August, 24, 2039.  The extrapolated curve is below, and you can click at the left for the data file.  The instruction file and various steps to make the plot were the same as before.