No plans to bring back Koburn, Earthlets. I feel he's kind of had his day.
Carlos and I have done a Dredd story called El Maldito for the Megazine that homages another favourite old character of Carlos's. No idea when it'll be appearing, but it's almost certainly the last Dredd story I'll do.
I will be returning to the Dreddverse, though, with a new series with Lee Carter - title currently embargoed - that'll be running next year.