It could just be off-gassing. The bubbler is not the definitive indicator that fermentation is complete: the hydrometer will tell you. If you take readings on three consecutive days and it reads the same all three, then you're ready to rack.
Plus, racking will leave behind most of the yeast, which will further slow any fermentation (less yeasties to eat any unfermented sugars). And don't worry if you get some serious bubblage after you rack to the new vessel - that will definitely be CO2 coming out of solution, almost certainly not renewed fermentation.