Not sure if this has been answered before (since the Search function has been disabled ...), but what happens to the units a building creates (like the Knights Templar) when an ungradable unit becomes available?

For example, what if I made a building that produces Warriors every turn -- once I learned Iron Working, would the building continue producing Warriors or would it start producing Swordsmen?

It would continue to produce warriors.

In the Age of Discovery conquest the Magellan's Voyage wonder produces a frigate every so often. Frigates are eventually upgradeable to the Man-O-War, but the wonder continues to produce frigates. I would just upgrade each new frigate to a Man-O-War in that city since it had a harbor.

ah, good point!

Thanx for the input! :)

You can also:

I. Complex

1. have the improvement/wonder be a necessary prerequisite for its successor

2. make the successor very inexpensive

3. have the 1st improvement/wonder expire shortly thereafter.

It's also useful to have the first improvement/wonders unit upgrade to the second's.

-or-

II. Simple

Just set the improvement/wonder to become obsolete at some reasonable point on the tech tree.

-Oz