At the moment, it is unsure whether or not there will be another
book in the Silverwing series, that involes Shade, Marina, Griffin,
and of course Goth. But, on Kenneths Oppels website he did say that
he had no immediate plans to write a sequel to firewing, which
means he's in no hurry, but he might. He said if he ever has a
great idea how to continue the story, he promise he'll write it.
And knowing Kenneth Oppel, he's full of great ideas, so there is a
good chance he'll possibly write a sequel. It just may take some
time, but in the mean time, if you havn't read Darkwing, you
should, and there is also a 13 episode TV series of Silverwing on
youtube or DVD. The TV series was cancelled though on the 13th
episode due to budget cuts. But, you never know, soon we may have a
a sequel!