Main reason Tanooki Suit brought back was to help with 3D jumping says Nintendo.

[Joelcool7]

I am guessing that the idea was to slow down decent. But I am guessing the Tanooki suit specifically was due to its past use. I don't buy that slowing down jumping was the only and real reason for the Tanooki suit come back. Nintendo stated they wanted Super Mario 3D Land to be the best of both 3D and classic Mario. To be a New Super Mario 3D, bringing all the best aspects of the past games together into the ultimate Mario adventure.

I'd say the choice of the Tanooki suit was probably made to give the title more of a classic appeal. Also the fact the Tanooki suit is appearing in Mario Kart 7 suggests Nintendo's two teams were working closely together. Miyamoto likely wanted the Tanooki suit to return and this was the perfect excuse he was waiting for.

Saying it was included to slow down jumping is probably simplifying the issue. I'm pretty danged sure that it was a much more thought out addition. The Tanooki suit is a major symbol of Mario and one that everyone remembers from the early days its return is paramount in making Super Mario 3D Land a true Classic/Modern hybrid mixing all the best of current and past Mario.