/snip
It would be like the 3.5 splatbook arms race all over again.
What 3.5 splatbook arms race?
Nearly every new class in a 3.5 splatbook was weaker than core. It was only when you allowed core classes to use the extra material (read clerics and wizards) that the power creep happened. And, all that really happened was the strongest classes got stronger.
If you actually used the new classes, there was almost no power creep.
And, you're presuming that the power cards will make any sort of significant difference to the power level of the character, rather than having a group effect. Since we haven't actually seen the cards, that's just an assumption.
You're also presuming that this is a test bed for whatever comes next. While, yes, they did use SW Saga to test out 4e, there are also a barrel full of products that are just one off sorts of things and not linked to the next thing.
Now, if, in the future, 5e is released and requires collectable cards, then you are perfectly in your rights to complain. But, piddling all over a product that some people apparently are looking forward to is just so negative. Vote with your wallet, but, why piddle on other people's fun?