When WP 3.0 came out everyone was excited about new default theme and I as many other WP developers started to use 2010 as mini framework for the child theme development of new projects. There is very big advantage to use default theme as a parent theme, because you always know that it will be updated frequently, introducing all the latest and greatest WP features and it will be always fast and secure.
But, nobody ever suspected, that 2010 will be default theme for such a short time :(
Questions to WP devs:
1. Will you continue to support TwentyTen at the same or similar level as Twenty Eleven?
2. Will you introduce new features and tweaks to TwentyTen, like the once Twenty Eleven got introduced?
3. It was nice, that Matt Thomas was dedicated to dev. of this team. Is he still working on it? Or perhaps other people will inherit this theme?
I think it would be nice if WP team would value all the time investment of WP developers and would continue to support Twenty Ten at least as Semi-Default theme :)