At some time in the future are we going to see extensions turned down because the 3 week/month course of study or medical treatment has been completed?
TLDR : Answer Summary
Concerns have been raised about whether future visa extensions might be denied after completing specific short-term courses of study or medical treatments. However, comments suggest that as long as the visa has been obtained, extensions should not be affected by the completion of these courses. Existing visa holders are likely to be 'grandfathered in' under current rules, and any changes to visa conditions will not retroactively apply to them.