If you were a documentation subscriber before we migrated to the new site, then no as your existing subscription would give you rights to access incubator until expired.
If you're a new subscriber to Advanced then yes you need to upgrade to Professional (only paying the difference!) in order for access to the incubator.
Please note incubator projects are team members personal works (not to be a deterrent as all are developed of the highest quality) made available to Professional subscribers. Most being developed by me (includes CB Articles). We do not have an official Joomlapolis release to integrate K2, sorry.
The incubator project is likely they only solution, but you're welcome to search Joomla.org for any sort of other integration if one is available. You're also welcome to edit the included articles plugin to point to K2 database if you'd like, but would take extensive editing.