Below are a few interesting graphs automatically generated from data collected from Google's Android Dashboards. They provide some insight into the dynamics and evolution of the various Android versions that there are, and may help predict future trends.
The following stacked chart show the history of the relative distribution among Android versions over time. The more recent versions are at the top. At some dates the top of the chart does not exactly reach 100%, this is because Google publishes only statistics for versions that have a 0.1% or greater share, and this small amount is sometimes visible. The data is gathered by Google based on devices accessing the Market / Play Store over a 1 to 2 weeks period prior to the publication date. Hover on the chart to get the exact published percentages at a certain date.
This graph shows the same data but that time the lines are not stacked and the share is summed by major version codename. This makes it easier to see individual variations. It is apparent here that the major versions follow long, relatively similar lifecycle starting with a slow growth in the first few month, then ramping up strongly and climbing for about a year to reach a peak, at which point the next major version is introduced and the share starts to decline slowly. In that light Gingerbread does not seem like an outlier and Jellybean will probably enjoy a similar long slowing down before it is superseded by KitKat.
This chart is a bit different and shows how quickly the different Android version gained support from the point they were released. It is assumed that any device that supports a given version is also retro-compatible with all versions before that. The horizontal axis is the time in months since release, which is assumed to be the date it first appeared in the statistics.
For clarity versions before Froyo are omitted from this graph and it is truncated to a 3-year period.