Game companies are showing they don't need more space than offered since very few games come close to filling up the space currently available.
On SD games, HD game have much higher-resolution textures and so need more space.
And are you seriously saying we should just not have any jRPGs? Nintendo already has enough trouble getting those sorts as it is without making them flat-out impossible.
I really want to see my Mario Kart everytrackfromeverymarkiokartever
So most games wouldn't come on 8GB cards, or probably even 4GB, they'd probably be 2GB or 1GB which would likely cost pretty much the same as discs. And if companies do need more space then it's there if they want it; the limit of what cards can be is pretty high.
First, no they would cost considerably more than discs. A 4 GB completely blank flash drive costs about as much as a 50 GB blu ray containing a movie, so the unit cost of blu ray would be much less. Expecting game developers to either jack up the prices by 50% or cut their profit margins by half is not going to make them want to make games for Nintendo. It didn't in the N64 days and it certainly won't today when there are two strong, established competitors on the market instead of one unproven upstart.
Second, the price goes up rapidly as you increase the size. A 8 GB flash drive would cost a couple times as much, a 16 more than 4 or 5 times as much, a 32 gb would cost as much as 2 games at least. The price for Blu-ray, however, does not go up at all until 25 GB, and even then it is not much more for 50 GB.
And that's a durable medium with no load times.
If load times are that big a deal they could stream data to internal flash memory in the background and load it off there. And it is possible to put discs in a durable housing, but it looks clunky so people tend to avoid that.
It is of no concern to me that companies have to spend a teensy bit more to offer this.
What I want is fun games, and I am not going to get them from third parties if Nintendo takes this approach.