Reviving this thread since we got a whole bunch of gaps revealed. Mostly of all these promos we're getting from the Dragon Majesty products.
Below is a list of un-released promos. Ones in bold are confirmed, rest are my predictions:
SM103 - Solgaleo GX
SM104 - Lunala GX
SM125 - Naganadel GX
SM126 - Ultra Necrozma GX
SM135 - Latias
SM136 - Latios
SM137 - Poipole (shiny)
SM138 - Zeraora
SM139 - Articuno
SM140 - Zapdos
SM141 - Moltres
SM142 - [Lost Thunder pre-release]
SM143 - [Lost Thunder pre-release]
SM144 - [Lost Thunder pre-release]
SM145 - [Lost Thunder pre-release]
SM146 - Leafeon GX
SM147 - Glaceon GX
SM148 - Champions Festival
SM149 - Reshiram GX
SM150 - Zekrom GX
SM151 - Salamence
SM152 - Salamence GX (full art)
SM153 - Kyurem
SM154 - White Kyurem GX (full art)
SM155 - Dragonite GX (rainbow)
SM156 - Kingdra GX (rainbow)
SM157 - Pikachu
There's no way this ordering will be accurate lol. Only promos we know of that are missing from this list are Sylveon GX, Tapu Lele GX and Tapu Fini GX. Sylveon is more or less confirmed an Alternate Art since Leafeon and Glaceon had their promo numbers revealed on the official website. I'm taking a stab the Tapus will be alternate arts too, otherwise they can be listed after SM156. (Eevee may also potentially be an alternative art - but I'm leaving it as a promo for now EDIT: It is alternative art).
Upon creating this I realised the White Kyurem/Salamence GX boxes, the Pikachu/Eevee Poke'Ball Collection, and the Island Guardians GX box all release on 2nd November lol.