The schedule of bundle update depends on Product Management team. This is not being done during release upgrade.
If a bundle's current version is 2.00.17 version then a customer clicks on a managed bundle and a pop up states that 2.00.18 version is now available, this does not mean that such version is now available. This notice only means that 2.00.18 version is still in progress. Our Product Management Team is still working on such new version. Once a new version is updated, all customers are updated. If it is a major release, then NetSuite notifies the customers through email.