I really don't think you'll have a problem getting these sets off ebay. Medicom has been saying their stuff is limited to "X" number of pieces for a long time now and frankly, I just don't believe them. From a business standpoint, it makes perfect sense to say an item is "limited" because nobody is ever going to know unless they work for the company. This isn't just limited to Medicom by the way, a lot of companies do this.
I don't think there's any difficulty finding anything at all, largely because of what you say. The hitch in the equation is the price. Not that anyone here wants to hear it, but my buddy in Japan hooked me up with the recent box set when it first came out, at cost. He's in Japan and got it through the club. I paid about $50 shipped, or maybe even less, I don't recall anymore. Anyone here can get the set providing they're willing to pay the ebay price. That's 6x what I paid and not a very nice price.
This stuff is as limited as the early McFarlane sportspicks chase pieces were. If you can get them at cost, you're so far ahead of the game. If you buy them at the peak, you're screwed, but that's how ebay thrives. With patience, prices fall as demand does and it does for almost all collectibles that are newer (vintage stuff being different) fall in price in time. The question is can you wait for it?
Most of the stuff done through the club is probably more numerous than the limited items like the Droids R2, but I don't think it truly hits mass production level. I think Medicom is keeping the buzz about the stuff while satisfying the needs of it's Japanese customers. Solicit for purchases to determine production size, make that many plus some extras and be done with it. No glut on the market in Japan, strong secondary market which drives many purchases in the primary market and you don't end up like McFarlane where the market is over or undersaturated. Plus you have no overstock to deal with and that's that. Different marketing approach than typical toys it would seem.
I think BrentS will end up with his items through the lottery and wouldn't be surprised if both addy's win, especially if my theory about solicitation to determine production run size is correct. Those that are in tough are those without a direct hook in to the Japanese opportunity to order.