Binary but not source compatibility
Xtext versions with minor increments are binary compatible with early releases of the same major version
That is you will be able to run any code, which was developed and compiled against API from 2.x with any 2.y (where y>=x) version. However you might run into compatibility problems if you try to compile or even regenerate source code which was developed against a previous version, because only micro increments (i.e. 2.x.y -> 2.x.z , where z >= y ) are also guaranteed source compatible.
Only if the major version increments API might be removed, replaced or changed in *binary incompatible* ways.