Does anyone see Ivan Reitman producing a new cartoon GB based mainly on Feig's movie/characters, instead of the original GB? IMO that is pretty much the only scenario where a new cartoon doesn't undermine Feig's movie to some extent.
GB isn't Star Wars, where there is enough audience to justify multiple branches of the franchise. It wasn't that long ago that GB was considered pretty much dead. There still hasn't actually been a new movie/TV released since then.
Even if they want to incorporate both new & old GB in the new cartoon, it still implies that they should have done more of that in the movie. They don't make cartoons aiming at 40yo fans of the original GB. If anything the cartoon would be the one aimed more at the younger/newer fanbase.