Here is a list of unreleased cards from page 2.
Quote from 'Moldyorange'
"Here is the current list of unreleased cards:
HGSS era (LEGEND era in Japan)
* 12 cards from Lost Link
**Tangela 3
**Tangrowth 4
**Relicanth 8
**Pachirisu 12
**Mime Jr. 16
**Mr. Mime 17
**Seviper 19
**Riolu 25
**Lucario 26
**Snorlax 28
**Zangoose 24
**Research Documents 37
**Lost Remover 38
**Lost World 40
* 22 L-P Promos
**Chikorita 5
**Cyndaquil 6
**Totodile 7
**Mareep 8
**Phanpy 9
**Teddiursa 10
**Master's Book 55
**Entei 62
**Suicune 63
**Raikou 64
**Ho-Oh 65
**Lugia 66
**Master's Key 68
**Kyogre 71
**Groudon 72
**Palkia 73
**Dialga 74
**Rayquaza 75
**Deoxys 76
**Porygon 77 (most likely these two are the promos for the 3 pack blister)
**Porygon2 78
**Shopping Pikachu 79 (probably not, but I just want a complete list of unreleased cards right now.)
* Would they go as far back as the 3 unreleased DPt-P Promos?
**chatot 32
**Jigglypuff 47
**Heatran 50
***Note, there are others in the DPT era, but extremely unlikely: 3 secret rumble cards, 12th movie commemoration set, 5 cards from the 11th movie set, random DP Promos.
My main reason for posting, is that, there are options that they can do. They did say, "Look forward to seeing more shiny Pokémon in upcoming sets" Those are the 11 of the 22 L-P Promos. And, EX Power Keepers contained cards from all of Generation 3's eras in japan, so maybe a filler set would contain cards from all over Generation 4's Japanese releases? Just somethings to think about. "