It's not a matter of "career stability." It's a matter of the printer you send work to only being willing to work with PSD or PDF. If no one uses Gimp, and none of your tools integrate with Gimp's native format, and no one else's tools do either, and no one can open the files in their email, making them less portable than Adobe files, then Gimp is a technical liability, regardless of its quality.
You are going to have a LOT more reach with Java for "career stability". That's why designers stick with it.