I think it's safe to say the original Bayonetta won't be bigger than the max size of a dual layer DVD. You know the disc the 360 version used. 

Ot: I have around 18 GB left. 

I got about 16 or 15 GB's left. My downloads mainly consist of updates for games and virtual console games though. Only thing that really left a dent in my space was Wii Party U, which I got for free

I still have around 20 GB left.... Mostly because I buy most of the WiiU games I own!

System Memory: 23 GB

USB Storage Device 1: 844 GB

USB Storage Device 2: N/A (don't really need one yet)

It has additional costumes, sounds, music, visuals etc and it's upgraded to 60 fps.  The odds of it being larger is pretty good unless there was a good amount of leftover space originally.

20GB. The only DL game I have on there is Pikmin 3. Since it was the free promo thing. But I have like 8 external drives if I needed it at some point.

I still have about 14GB left so I can download plenty of VC games still and maybe one or 2 of Nintendo's first party games I didn't buy at retail.

I just worry that, as Ataraxias suggested, the new costumes, items, animations, sound effects, and potentially less compressed assets or reused ones for better disc seek times could combine to make it bigger than the 360 release. 

I am at 840MB left, there was no less than 1 gig option so I chose none :P Plus I have had to remove stuff off of it to make room so yeah... it really is none.

No offense but I believe you are completely wrong.  It is better to pass the cost to the consumer when it comes to storage.  So you want them to increase their internal storage space right?  They use SSD for their internal storage.  SSD are far more expensive than a regular external hard drive.  Is it too much to ask of consumers that are heavy digital users to go out and buy a 1-2 TB external drive for under $100.  This isn't Microsoft charging people outrageous prices for proprietary hard drives for the 360 or Sony doing the same thing for proprietary SD cards on the Vita.  This is Nintendo giving the consumer the option to vastly expand the storage space for under $100.  I suppose you might be too lazy to buy and hook up an external drive.  I for one haven't done it yet but I still have a little space left with a decent amount of stuff downloaded.