What worries me is that if they lower the quality of their cards for all their games to allow them to make POD expansions. From what I heard, Mansions of Madness board game cards are thinner amd weaker than the ones from Arkham horror.
I wouldn't worry about it, as that seems very unlikely to happen.
The POD cards are indeed thinner (and thus probably weaker) than the non-POD cards, but if you read this thread closely, you'll find that normal Death Angel cards remain high-quality thick textured cards. It's just the POD expansion that's thinner and lighter. That's why people say you need to put them in card sleeves so you can't tell them apart on sight or by touch.
Similar statements can be found at the page on the Mansions of Madness POD expansion, where it specifically mentions that the POD cards are thinner and that the POD expansion includes reprints of some cards from the base game so that you can't tell by the backs of the cards which ones are from the expansion.
Every indication is that FFG expects the POD expansions to be thinner stock than the normal cards, and is _not_ changing existing (or future) games to match the POD. Since the POD is not done by their normal printer, it may even be that they couldn't match the thickness or texture even if they wanted to.
The whole point of the POD is to cut costs and risks on mini-expansions, so that they can print things that would otherwise never see print because they'd be too expensive (or not sell enough copies). Given the choice between a micro-expansion either being on thinner cardstock, or not existing at all, I'd choose the lighter cards.