Found this posted on Sonic CulT. It's a blog where some guy, who claims he knows a lot about the development of this game, is giving some info about the development history. It's pretty negative.
http://bossrush.blogspot.com/2007/03/nights-2.html
Consider this: work didn't even begin on this Wii version until around Sept/Oct 2006 (up to that point it was being developed for X360/PS3 until those platforms were canned against Iizuka-san's wishes) and it's due out this autumn-winter. Take into account the 4-6 week Nintendo submission time and you're basically talking about roughly a year's actual development (i.e. coding; not pre-production) time.
The fact that it's being made at all is not even a good sign, for this only came about due to a combination of Iizuka-san's efforts and Sega's managers finally relenting and giving Sonic Team a brief break from the monotony of Sonic related development (e.g in Sonic Team USA's case Shadow The Hedgehog) - there is no genuine expectation from Sega's bosses that this title will perform well and thus they will spare little development time, thought and marketing spend on it. Furthermore I know Sonic Team, by which I mean I know them in person, in a professional sense. I know how they work, and the (difficult) conditions they work under.
....and a post he made in the comments section, where he claims he played it already:
Also, let me take this chance to clarify a few things that I have been asked by people regarding this post. Firstly, I have actually seen and played the code (both the Wii version and the older X360 version last year). Secondly, and related to that, there is the issue of supported platforms, which is a bit complex so let me start from the beginning.
1) Iizuka-san originally only wanted to make NiGHTS 2 on the X360 and PS3 - his vision for the game, which was a pretty grand one, could only be done on those platforms he argued and development started on them, even though the actual GDD was still being fleshed out and a Wii version was being considered.
2) By the time of TGS last year there were playable ROMS on X360 and the general response to the code was not positive. At this stage the directors questioned the X360/PS3 SKUs and suggested that Wii may be a better choice. Iizuka-san was against this because it would mean reigning in certain aspects of his design, but nonetheless Sega Studio USA (AKA Sonic Team USA) drew up a comparison doc for Wii and X360/PS3 version pros and cons. The summary of this was that they could produce a quick Wii version by FYO8 (2007) and then go onto a different version of NiGHTS 2 on X360/PS3 for FY09 (2008). By different I mean, different like Sonic The Hedgehog on X360/PS3 was a completely different title than Sonic Wii.
3) This was all up in the air for some time, and in the meantime Iizuka-san was convinced to start working on the Wii version primarily, leaving the other SKUs behind. Essentially they were canned, but there was and still is the option to continue as suggested and work on those versions once the Wii version is finished and released. In other words, NiGHTS on X360/PS3 is dependant on the success of NiGHTS on Wii.
So there you go.
Whether or not he's telling the truth is anyone's guess....but what I did feel happy about is that Iizuka seems to still have a lot of passion for his work, as opposed to the popular view that Sonic Team is just in it for the money. SEGA, yes, but Sonic Team themselves, no.