The Ubercart and commerce modules are both growing in user base for Drupal 7. In April of 2011 I wrote about e-commerce for Drupal 7 at that time Ubercart had 900 sites on Drupal 7 while commerce had 500 sites.
Over the last 6 months the growth story is....pretty close.
See the raw data of this chart.
When will the Commerce module for Drupal 7.x report more users on its project usage page than the Ubercart module for Drupal 7.x for 3 consecutive weeks? And of course one of the outcomes is "never."
If the 3 weeks are over a breakpoint in the outcomes then the first day of the first week of the 3 week period will be used.