If you have a version # hardcoded (like in this example) and don't have any other info in the pom conflicting with it, Maven will use 3.0.5 forever. It is stored in Maven Central and Maven can pull it down years from now. It is also stored in your local .m2 cache so Maven doesn't have to keep downloading it from the internet. You can see the list of
Spring core versions Maven has available. If you page through, you can see there are 62 versions going all the way back to 1.0.
If you want Maven to pull a later version, you need to update your file. Or you can specify a more generic version like LATEST and have Maven take care of that automatically.