I have no idea whether SE has any plans to introduce "get it now, or lose the chance forever" cards for Triple Triad. What I DO know is that if such cards exist, or come to exist, Triple Triad will lose a lot of interest for me. I'm a collector; if I don't have at least the capability of obtaining ALL the cards, I'll have precious little interest in obtaining ANY of the cards.

It's the same reason I don't care much about minions or mounts. There are some now that can never be obtained again. My collection can never be complete, so why bother to collect at all?