This is my predictions:
-Bowser and Toon Link are going to be the most common, similiar to Yoshi/Kirby/DK was at first.
-Sheik, King Dedede, Megaman and Sonic are going to be widely available, similar to Fox/Samus/Zelda from Wave 2, but I´m expecting Megaman and Sonic to be bought in bulk and be hard to find, even with new shipments. There is also enough time for people to preorder, and scalpers would have a smaller second hand market. Of all this, I expect King Dedede to be the harder to find.
-Ike is going to be the rarest one for sure, get it kids.
-Toys R Us are going to have A LOT of Lucarios in the first day, at least 16, how many of those are preorders is going to be the main issue, but expect at least 6 to be sold to the public, TRU has history of overstocking exclusives.
-Shulk is going to be "available for people who pre-ordered" and maybe have one or two more at launch, but a week or two later they´ll have lots of them, and once those are gone they are going to be gone for at least a year. Expect them to sold-out fast at launch and then suffer to get one without preorder.
-Rosalina I have no idea, Target is weird.
-Best Buy will have trouble fulfilling all the Meta Knight pre-orders, specially for in-store pick-up, I recommend either go to a Best Buy you really trust or enter your shipment and keep track of it, send emails about it near launch and be sure you get it shipped.