Updating from any version of Mockups for Desktop to Mockups 3 for Desktop is free. Minor-version updates are also free (so 3.2, 3.3, etc.). There are no maintenance or renewal costs in order to keep using the software.
Major-version updates will have an additional cost. As updates are not required, you will be able to continue to use version 3 if you don't wish to purchase a major version update.
We will continue to offer support for version 3 for at least 12 months after Wireframes for Desktop is released. However, historically we have continued to support versions for much longer than the minimum time noted in our EULA. We are currently still supporting customers who have chosen to keep using version 2, even though version 3 was released in March 2015.
There's no exact date available for the release of Balsamiq Wireframes for Desktop, however it's planned for sometime in 2018 as shared on our blog post. Exact costs of the new version will be available when we are closer to the release date.
When we ship Balsamiq Wireframes for Desktop (which will be native and may be sold via app stores), we’ll try to give existing customers a discount for updating. As licensing restrictions in app stores are changing quickly, we can’t promise anything at this time.