Speculation:
SE has had a previous pattern of introducing songs. Most songs are given to us every other level on the odd levels. Threnodies, Carols and Etudes are given to us every other level on even levels. There's a few slip up's here and there (some related to adding songs after the fact), but for the most part this is true.
As SE raised the cap to 80, we see a similar pattern, in that we received new songs every other even level (it switched). Knowing their previous pattern, it would be likely to assume that they plan on continuing this until the cap. This leaves us with 9 more generic songs (82,84,86,88,90,92,94,96,98). This most likely applies to: Requiem, Minne, Paeon, Minuet, Madrigal, Prelude, Ballad, Mambo, Elegy, and Similar Songs
A few bar-status songs were released out of cycle and also broke the one-song per level rule (actually the Unique Songs they were accompanied by were the ones most likely broke that rule, so this part might not apply - see below). The standard release is assumed to be that of the previous set, every other even level. Some of the songs in the dats have signature parts that make them appear to be bar-status types (specifically, they all end with hexagonal gems like all other bar spells). These songs might be released under the generic song list above. This likely applies to: All bar type songs, in addition to these songs in the dats - Chocobo Hum(bar-??? has stars), Jester's Operetta (bar-silence), Devotee Serenade (bar-??? has rainbow-microbes), Cactuar Fugue (bar-??? has blue balls), Moogle Rhapsody(bar-??? Has purple/pink clouds), Protected Aria (bar-??? has hearts)
However, since Carols were out of tier previously, SE could do the same here. Since it was already pointed out that dats for Tier II Carols are already in-game, we can presume that we could get 8 additional songs (or more) on the odd levels. This most likely applies to: Carol , Etude, Threnody
Unique Songs have always been released out of order or paired with other songs. Songs of this type have various effects. This applies to: Mazurka, Virelai, Hymnus, ???(Colorful music staff with a few notes surrounds character, ends in a flashy halo of light), and future songs
Lullaby is an odd element, in that it was released on both an even and odd numbered level in addition to breaking the one-song per level rule. It is likely to also be considered a Unique Song. We may also presume that we may get this additional song at any level, if at all. This applies to: Lullaby, Lullaby II (?)
While this doesn't mean these are the only songs to be added, it also doesn't mean we are guaranteed to get these songs either. My goal wasn't so much to point out specifically what song we might get, but to identify the previous pattern used and the likelihood that SE may use the same pattern in the future - then to categorize which songs might belong to which pattern. Hopefully this shows that there is the possibility to add all/most of the songs in the current dats, as well as an additional Threnody or Etude Tier and any new Unique Songs SE could come up with.
Or speculation could be blown apart and SE could just give us another 20 Requiems.
tldr; version: Based on previous patterns, SE still has room to add 9-Generic/Bar songs, 10-Elemental songs, and any number of Unique songs.
Edited, Jun 26th 2010 4:56pm by Asmoranomar
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Asmoranomar - Diabolos
BRD/RDM - Song Cast Time Setup
BRD/WHM - Wind Buff Setup
BRD/WHM - Wind Debuff Setup
BRD/WHM - String Buff Setup
BRD/WHM - String Debuff Setup