Just a way to milk more money out of the original series. Yes it does tarnish the original series albeit indirectly.
I can agree with this to a certain extent, because it wasn't like Saul was this big character that all of the fans loved. At least not to the point where the creators and writers felt like they had to give the world more of him? Because of that, it does seem like they have created this series just to milk Breaking Bad. But on the other hand, if you have low expectations for Better Call Saul it is bound to surprise us and be better than we'd originally think.
Yeah I think even though this show is partly being produced to continue on the Breaking Bad legacy in some way, it will end up exceeding our expectations of it since our expectations remain at a pretty much flat line level right now. But Vince Gilligan is heading the project and he masterminded the greatness that is Breaking Bad, so we should have some confidence that it will turn out decent in the worst case scenario. I would surely love to see some flash-forwards in the show too, where we get to see what becomes of Jesse Pinkman and even Walt's family. That'd be sweet!