My understanding of the collectible market terminology is this:
1-Retired--means thet all the molds of a certain piece are broken and that piece (numbered or not numbered) will never be produced again.
2-Revised--means that a revision has been made to the piece and a new mold is now being used for production, but it is still the same piece only a variation of it.
3-Taken out of production--This means that a certain piece is no longer being produced(for whatever reason the manufacturer has), but the molds are not broken and that particular piece may be brought back into production at some time in the future.
So in a real sense, true retirement of a piece depends on if the molds are destroyed or not. It really has nothing to do with numbering. Numbering is used only for limited edition purposes, but retirement can apply to both limited and unlimited editions.

"the lightkeeper"