Where's this notion that microSD is replacing normal SD cards coming from? All applications (camcorders, cameras, laptops, 3DS, etc.) where the expectation is that you'll swap the card out with some routine use either normal SD cards, or in the case of the Vita a proprietary format with similar dimensions. Only applications where thin profile has priority and the expectation is the card will rarely be removed from its fully enclosed, dare I say armored, receptacle.
It's not hard to understand why if you've handled microSD cards, they're relatively fragile and not suited to taking abuse from routine handling. Switching the Pandora over to primarily using them, and for that matter neglecting to make GNU/Linux a priority, would involve radically changing the projected usage profile away from the niche that actually serves to justify its existence.