This may seem like an odd question, but do publishing companies ever find themselves without something good to publish? What do they do then? Not publish? Or publish something mediocre?
Depends on the company. Larger companies get enough submissions that they can fill their schedule with enough good titles to satisfy their sales department.
Smaller companies do sometimes find themselves without manuscripts they feel strongly about. My company was often in that situation—especially the first couple of years.
What they do about it also depends on the company. We chose not to publish anything, rather than publish something we weren't ecstatic about. Other companies insist on putting out a book on their regular time schedule, so they'll publish something less than wonderful.
Now my question for you is, why did you ask this question?