Victor Ireland, president of Gaijinworks, and previously Working Designs, which localized Growlanser Generations, recently commented on the state of localization for the series.
When asked about whether there may be any future Growlanser-related projects, Ireland answered: “We can’t even get Atlus/SEGA to re-license GL2/3 to us for PSN release, so other chapters are very unlikely.”
This likely refers to Growlanser Generations, which was a North American compilation release of Growlanser II and Growlanser III. However, the original plan at Working Designs was for Growlanser II and III to be released separately. Either way, it seems that the decision on future Growlanser series lies with Atlus.