I've been trying to collect all the Kanto/Johoto cards for some time, so I'm going to have to say yes. I've been looking on eBay and at stores, and I can't seem to find them all.
That is because the old cards are unplayable in the league. So they try to refresh their stock with every new set, not only because of the league requirements, but because they always put out adds for the new sets of Pokemon cards.