Yes, there very much will be. This is according to Michael Ausiello.

Question: Wow! Torchwood: Children of Earth pretty much ascended to a BSG level of fraktacularness. Is there even the slightest chance that the franchise will continue? Personally, I can't see it coming back from the emotional shock at the end. --Amy
Ausiello: First off, we're only up to Part Four here in the States, so watch the spoilers, missy. Second, yes, Torchwood will most likely live on, according to T-boss Russell T. Davies. "I’m fairly confident the series [will continue] in some shape or form," he says. "I will just sit down and invent new stories and characters -- that’s what I’ve spent my entire life doing." Wait a sec, new characters? Jack will continue to be the show's central hero, right? "Oh, I would think so," he says. "I would hope so. He’s absolutely fundamental to Torchwood." (For more on the emotional shock that Amy referred to above, come back here tonight after Part Four airs. Trust me.)