Dancing Stage Supernova is missing content which is going to be implemented in the upcoming (japanese and american) Dance Dance Revolution Supernova games.
The second most important rule is :
Nothing so far suggests that 'unlockable' songs exist in Dancing Stage Supernova.
Things to consider :
* The only Dancing Stage (or american DDR game) to feature hidden songs is Dancing Stage Euromix. Every month, the game featured a different 'Internet Ranking' Nonstop Course, which always included 1 hidden song, which wasn't selectable in any other mode.
At the end of the 5 weeks, Konami released a code to arcades who participated in the Internet Ranking program, which added the 5 songs to the normal song selection screen.
In January 2002 Konami released an update for Euromix, which changed some of the background videos. In the update, all 5 songs are unlocked by default. The update is identifiable by changes made to the Silent Hill and So Good videos. Machines that came pre-installed with the new software have a blue banner (instead of a pink one), which boasts '5 New songs'.
This is the only time Konami have released an 'update' for any Bemani game. The update was released in order to alter some background images that could be deemed offensive, not to add new content to the game.
In Japan, DDR 4th, 5th, 6th, 7th Mix and Extreme all contained unlockable songs. The songs are included in the game software when it ships, but do not appear on the song selection screen. Konami traditionaly waits until the excitement of the game's release has died down, and then releases a code on it's website, which when entered by an arcade operator, will unlock a few specific hidden songs on the machine (usualy 4).
Since the release of the last DDR game, Konami have implemented a new system in all of their Bemani games, called E-Amuse. Players each obtain their own E-Amuse pass (a magnetic card, similar to a credit card), which they insert into the machine, at the beginning of the game. The card keeps track of that players' name, high scores, which songs they've passed, and which secret songs they have unlocked. Some songs are only playable by players who have that song unlocked on their E-Amuse card, which means you usually have to spend about £100 on the game, before you can unlock (and play) all of the secrets.
After a certain ammount of time, Konami release a code to arcade owners who do not have E-Amuse enabled machines, which allows them to unlock the hidden songs for all players.
Firstly, Konami always uses unlock systems which maniuplate the money generated by the machine, either by players coming back to play it every month when new songs are unlocked, or by pumping money into their E-Amuse card, to earn all of the unlocks themselves.
This rules out 'dancing on the menu screen', which was a system tailored for 'In The Groove' (a game which players care for, but most arcade owners hate). If DDR used this system, then all the unlock codes would be discovered overnight, by dedicated players.
There won't be an 'update' either. Konami will only release an update if they feel that the game is in danger of losing money. They won't release one to appease players, or to try to improve the game. That would cost much more than it could possibly make, and only around 2% of machines would actually get updated.
The songs will definately NOT be unlocked based on player achievements, or by hitting certain scores. Reasons for this are explained below.
As with all new Bemani games, the assumed method of unlocking songs is via an E-Amuse system. Konami Japan have already confirmed that DDR Supernova will use the E-Amuse system, and have installed it on location test machines.
Dancing Stage Supernova cannot use the E-Amuse system, and was released in Europe long before development of DDR Supernova was completed. It is certain that the japanese game will have more features than the european game. It is unknown whether new songs are still being developed for the japanese game.
When it comes down to it, the realistic options are :
A) DS Supernova does not contain any 'unlockable' songs.
B) Unlockable songs will feature in DDR Supernova, but not DS Supernova.
C) Supernova already contains hidden songs, arcade owners will be told how to unlock them in the future.
Given Konami's overall business strategy, I think (B) is the most likely. That's just an educated guess based on everything I know about previous games, and Konami's worldwide view on the game.