I would be OK for a while, until I learned everything there is to learn about the ones I have. Then I would be very sad, I think.
I suppose any good deck is somehow endless, so you never stop learning it, but another way of learning it (for me) is comparing it with a new one. I was never a fan of the RWS (the Original edition laid forgotten in my bookcase until mere months ago). However, I have learned to appreciate it thanks to my other, very different decks. If there are no more new ones... I shudder to think about it.
But if one thinks about it, for many years one deck was all there was for people. Tarot readers usually had only one deck, and only one style of reading it...