EDIT: 3.0.0-rc9 had return type as Stream<JacksonModule>, changed in rc10 back to Collection<JacksonModule>.

Due to changes in registration of Jackson Modules (Module in 2.x, JacksonModule in 3.x), it is now possible to get access to actual modules added/registered, and not just ids.
So it makes sense to change accessor as well.

One note: while 3.0.0-rc1 - 3.0.0-rc8 had replacement as

public Collection<JacksonModule> getRegisteredModules();

and 3.0.0-rc9 as

public Stream<JacksonModule> getRegisteredModules();

we will change this further in 3.0.0-rc10 to

public Collection<JacksonModule> registeredModules()

for up-to-date naming ("getXX()" only for Simple Property accessors).