When you installed 2.06+ (build 150611) before Jun 12,2015 you won't be offered the update. The other updates are not offered either.

Since 2.06+ received stable status only a few days ago the online update distribution seems to be still on hold.

When looking on such big fixes on the first day
Changes from 2.06+ (build 150611) to 2.06+ (build 150612) Jun 12, 2015
-Fixed issue: Unable to add answer options/sub-questions or to edit quotas (Carsten Schmitz)

I wouldn't label 2.06 stable. For surveys which starts soon, you would normally stay on 2.05 for at least a few weeks to months.

To encourage more people to update a multi tier concept should be considered.
To illustrate a multi tier concept take a look at the distribution concept of cpanel
documentation.cpanel.net/pages/viewpage.action?pageId=2719905
LTS Long-Term Support. If you do not wish to upgrade, you can select version for as long as it is supported
STABLE This version has received considerable public exposure, testing, and verification. Published least frequently.
RELEASE This version is feature-complete and well tested. It contains all intended features and functionality. New installations default to RELEASE. Published more frequently than STABLE.
CURRENT This version is tested and verified, but it may not contain all of the proposed functionality of a release. This tier is similar to the "release candidate" tier used under other publication schemes. Published more frequently than RELEASE.
EDGE This version only has rudimentary testing. The features are subject to further modification. This version usually lacks official public documentation.
Due to the dynamic nature of EDGE builds, only use EDGE to test for compatibility and functionality in a controlled environment. This tier is not recommended for production servers.

With the current concept the online update won't deliver any update at the moment (because 2.06 was marked stable).
Please correct me if i am wrong.