A much better read than endless ramblings.
PART 1:

Let's start with the screenshot above. Set in a snowy level (similar, no doubt, to many of the levels in World 5 of the original New Super game), the most noticeable thing about this screenshot is some of the color choices on display. As you can see, the pipes are pink instead of green or red, the brick blocks are grey instead of reddish brown, and the Pirahna Plant and Koopa Troopas are solid gold.
The grey brick block harkens back to World-e of Super Mario Advance 4: Super Mario Bros. 3. This world, which made use of the Game Boy Advance's e-reader peripheral, is the only Mario game (until now) to contain grey brick blocks, which could only be destroyed by Hammer Mario or by Tanooki Mario's statue form. This could perhaps indicate that one or both of these powers will be making a return in New Super 2.
There's no telling for sure just yet, but the golden enemies may perhaps have something to do with the Super Star item, which makes Mario invincible for a limited period of time. Are there perhaps invincible enemies you have to dodge this time around? The screen is also full of sparkles, further indicating that some special effect or something similar is in place, disrupting the normal state of things. It's also possible the golden Stop Watch from Super Mario Bros. 2 is back, which allowed Mario to briefly stop time and freeze everything on screen.
And does it look like Mario perhaps just bonked a hidden block? If so, that could be the cause of all this golden mischief, as well as a happy confirmation that hidden blocks are back. Or maybe all these shiny enemies are somehow related to the Gold Fuzzy from Paper Mario: The Thousand-Year Door (we somehow doubt it though).