Glen wrote a bunch of related Black Company stories, over the past 15 or so years. He said somewhere that some of them never got published, because they were written for proposed anthologies that never came to fruition.
Mainstream anthologies of heroic fantasy basically dried up. But now, small presses are filling the void by e-publishing new heroic fantasy anthologies, and offering print-on-demand paperbacks. For example, the 4 Horsemen Universe is a popular series of anthologies and novels of military sci-fi, and now they are branching out to do similar e-books and POD paperbacks of heroic fantasy.
So my guess is that Glen's agent has found renewed interest for his short stories, and hopefully some more appear in the next couple of years.