IMHO, our order of likelihood to see a port of NiD:
1. PS3/360 - Easily a downloadable title, could feature online leaderboards, 2P versus matches of the NiGHTS and Reala battle, raise and share your Pian data from A-Life, customizable soundtrack (*COUGH*LUCID DREAMING PROJECT*COUGH* okay, sorry, but you know I had to include this shameless self promotion a little bit

). Seems like the best bet based on the reduction in price from physical distribution and the ability of the hardware to run something like NiD port code.
2. PSP - Seeing as the PSP is just a miniaturized and powered-down PS2 hardware setup, I can definitely see this happening. It's one of the few games that makes sense to play ON THE PSP'S SINGLE ANALOG STICK NUB.
3. 3DS - No idea what coding is like for this, but if Sega's looking for a "hook" to port the code and have an improved feature set, NiD in 3D would be a no brainer. If the 3DS has the kind of power they've been tossing around (near-Wii-level graphics), I can't think of why this wouldn't get swept up in the port-of-old-classic-games-frenzy that's going to launch along with the hardware. Oh, and controlling NiGHTS with the touchscreen would be full of win.
4. Wii - Unforutnately, while I'm sure the hardware is probably capable of running it, it's less likely because of the digital distribution model for it being near-nonexistent (just not enough space on the Wii, no built in HDD). However, it would still be awesome to have and I would totally support it!
Having said that, I've got two things I now have to work on:
1) coming up with something music-wise just for this campaign
2) getting my...special present ready from the Lucid Dreaming project for NiGHTS's 14th birthday.
Even if NiGHTS doesn't get all the bells an whistles for the 15th Anniversary, at the very least it will be getting something from the fans. Sega, would you be so kind as to meet us half way and port it over to current systems? My generation was lucky enough to have the chance to experience this game growing up, and in my childhood innocence, I took in this amazing game. With so many other less-imaginative games that exist, don't people now deserve that same opportunity?