Got some info from work, nintendo Eshop cards are going back on sale Feb 23. - Mar 1st in Best Buy Stores
20% off reg price. This means if you were to buy a $50, you pay $40, $100 = $80 and so forth.
(forgive me for the scale of the photo)
I plan to buy enough to prep for Smash bros and mario kart at the least. may also for DKTF, heck of a deal if you factor in the deluxe digital promo!
keep this in mind, if you're looking to buy DKTF, with this promo you could buy a $50 for $40, purchase the digital version on eshop and only have to pay the tax (if applicable), saving you $10 vs buying the disc.
I know some of you prefer the disc, but just a money saving tip. Also you'd have to wait a couple days, since the sale would on 2.23 and DKTF releases 2.21