When J!1.6 was announced, I though that many of K2's briliant workflow and usability features might had been incorporated (or even K2 itself replacing com_content). It didn't happen. When J!3 alpha was lauched, I hoped more of it was incorporated in the core. Not again.
K2 has been, by far, the best "off-the-shelf" com_content joomla has had in years - seblod is too complicated and Zoo is not integrated with many other extensions, standard com_content is really a usability challenge for customers both in the front and in the backend and the other CCK's are in between these.
K2 really adds value to Joomla and I simply feel it's getting further away from joomla in J's most recent releases: more and more extensions rely mostly on com_content (for example, multilanguage, native translation or light cck's) and if one has such needs for customers, well, then it's "plain vanilla Joomla com_content" or wordpress (which, by the way, customers love).
So I think this has been mostly a missed opportunity: a briliant content creation component that should have become part of J! core or at least most it's solutions incorporated. And joomla (apparently) becoming more and more like Drupal in terms of complexity and less "end-customer" friendly.