Is this is a bug or a feature? On both APEX 4.1 and 4.2 (apex.oracle.com), when an item is renamed [verified only with Text fields], the DAs are disconnected because the Item rename is not effected in the Item's DA(s). However, the DA can be reconnected by editing the disconnected DA and renaming the Item(s) in the When attributes. I suppose this also means that DAs can be "reassigned" between Items by editing them (the DAs) to change the referenced Item name(s).
The behavior I expected was that the DAs would remain associated with the Item even though renamed. Likewise, when copying individual Items from one page to another, I wish the DA(s) were not "lost" but copied as well.
A word of caution: Sometimes the DAs seem to be duplicated by the renaming of the Item and or ... So you may need to clean up / delete "extra" copies of the DA after you rename. I've experience this on both 4.1 and 4.2.