I can't help but feel quite disappointed if this were true . I don't know how the market would react. On the one hand many people that did not purchase the Wii U did not experience these games, on the other hand I can see backlash forming from the announcement of too many ports. Another issue is that a bulk of these titles are 2D side scrolling games including many of the newer titles, there is simply not enough variety here. I am also not sure if third-parties will really remedy this situation, since Nintendo themselves have, for the most part, been the biggest pushers of their hardware with software. It was certainly detrimental for third-parties when Nintendo left them alone in the initial days of 3DS and Wii U. In addition, much of the third-party content we know of up to now has been ports, which would make for excellent support titles, but I am not sure how many systems they could really move.
As for NSMBU (which, btw, is being rumoured by some that correctly predicted Monster Hunter Worlds and Dark Souls Remaster), I don't know why they cannot, at the very least, create a new game here. An enhanced port of a large-scale game like Smash would have been acceptable, since those take a long time to make. However, NSMB, for the most part, simply needs a couple level designers and a few programmers (Nintendo made NSMB2 and NSMBU in the same period); Mario Maker, which was a retooled and more user friendly version of their internal level design system, basically demonstrated that it is not a resource intensive process. This particular rumor, if true, would be a real shame because it would mean that Nintendo is publishing a direct port of game that was originally criticized for playing it way too safe and lacking major innovation (and one that as a launch title did not manage to sell the Wii U concept to the masses).
I really hope there is more than this (old first-party ports, new first-party side scrollers plus some side-scroller ports, old third-party ports, LABO) if Nintendo intends to move 20 million units or even sell as many units as this year, because with this rumoured lineup...I just don't know.