This will depend on the management. They generally don't like paying people's salaries unless there is some point. If the company plans on taking the game further (expansion or engine licensing), they will probably assign some developers to continue tweaking. Otherwise, I think the game gets bug support only.

Developers in their "free time" (after hours) may want to try things out. In this case, the developers must be careful with the Configuration Management process (baselining code), anything they change cannot be checked in. Essentially they will need their own copy of the code and build area. Generally, this is a big PITA, and if they do get the managerial go ahead to check things in, they have to worry about merging files with support patches, testing, etc.

The only reason I can see this happening is if a developer is really attached to the game, and maybe slightly disappointed in the end result.