Gearbox boss Randy Pitchford is on record as saying that June's Forever wouldn't be the last we'd see of Duke Nukem, and the studio is now seeking feedback on the game, presumably as part of its planning for Duke's next outing. You don't even need to have played the game to give your feedback - it appears Gearbox is as interested in why you didn't - and the survey only takes a few minutes. We'd fill it out ourselves, of course, but we assume Gearbox already knows our thoughts.
Source: Gearbox