jayderyu specifically stated updates, not new versions. If you buy Unity version 4, you get all version 4 updates. You don't have to pay when 4.1 becomes available for example. However, when 5 comes out, you will have to pay to upgrade. Construct and Construct 2 have separate licenses just like Unity 4 and Unity 5.
All Construct 2 updates are included when you purchase a personal license. If Scirra decides the next version is a major milestone and creates a Construct 3 version, I would expect you would have to pay an upgrade cost as well.