At this stage, the version number increases from 1.0.0 to 2.0.0. Now this is where you need to look out. At this stage, things might have changed so much that constructs have been renamed or removed. It might not be compatible to earlier versions. I'm saying it might because a lot of software authors still ensure that there is a decent backwards compatibility, but the main point here is that there is no warranty, no contract, guaranteeing that it will still work.