Netbooks and Gazetters?
Hm...
"Gothic Earth - London", a city book (might work well as some of the people here are already working on Paridon, doing some resarch in London and some would've liked more technology there, but were stoped by canon. But London has it all.)
"Gothic Earth Gazetter - (Countryname)" (I would suggest the British Isles, Germany and Egypt, in that order)
"Heros and Monsters of Gothic Earth" a NPC-book (we might take the characters suggested in the thread here atthe fraternity as a basis)
might be combined with
"Behind the Masque - Races of the Gothic Earth" (part monster compendium, part Players Handbook, creating/explaining the background for standard DnD races and creatures for Gothic Earth, for example one of my group is an elf from Ireland, but all other members still think him to be human because of his glamoure-masque)
"Masque of the Jade Dragon", fan-made and to fit the current setting of Gothic earth, not the earlier period suggested.
An Adventure for Gothic Earth (maybe based on a not so famous book, like A.C.Doyles "The Maracot Deep"?)
As for the time area:
I for my part am against a change of the time. We are talking about "Gothic Earth" and not "Horrors of the Modern World". I must admit that "The Great War Project" was done well, but it wasn't very Gothic.
Maybe a future netbook (but not one of the first) could handel different timeperiodes of Gothic Earth like it was done in one Dragon Magazine article a long time ago. But as you see below, my Campaign is destined to end the year, Gothic Earth starts to become "ungothic".
If time-paradoxes occure, hey, it's fantasy, and Gothic Earth is not our "Real World". So you need not concern with changes at all. Killed the President? A doppelganger takes his place. Characters using player-knowledge? There is no gold found in New Mexico where the characters are looking (but apretty strong native american mummy)

. Problems solved, and to me it's part of the fun.
And it's more easy to plan ahead: In the modern world you face the same time- problems as in the victorian age. Your players accidently killed George W.? Now what? Same problem...and I don't know what's going to happen next week...but i do know what happend in 1893 after my game completed 1892.
I for my part started the Game in 1892 and intend to end my campaign in 1914.
These are 3 of the 4 major artifacts of my campaigns metaplot.
(Players of my Round keep your eyes shut!)
The Cassandra-Tablets - The secret Leagacy of Heinrich Schlieman
Forbidden Lore: When the German archaeologist Heinrich Schlieman died in 1890 it was not because of his illness or the operation. Agents of the Red Death followed him to Greece and killed him but failed to claim the price they had come for, something Schlieman had found and out of fear kept hidden ever since.
When Schlieman unearthed Mykene, he not only found the mask of Agamemnon, but also clay tablets that bore inscriptions, prophecies by the seer Cassandra to be exact. Besides the fall of Troy and her own destiny, these prophecies had a specific theme: the past and future horrors enacted by an ancient unspeakable evil entity. The tablets speak of great wars and annihilated cities, but they also speak of the possibility of banishing the evil by taking it through the Gate of the Gods.
Before his death Schlieman hid the tablets and literally took them with him into the grave.
The Canopic Jars of Djoser
These jars are supposed to contain the organs of Djoser. Maybe they still reside within a hidden cache of Djoser’s pyramid, but maybe they were scattered across the Earth by greedy graverobbers.
Forbidden Lore: As Djoser was still alive when Imhotep conducted his immortality ritual, the jars only symbolically contained the kings organs. But they were a vital part of the ritual and they contain something: the first spark of the Red Deaths essence. From his very first moment, a fragment of his power was woven into these jars. Should they ever leave Gothic Earth The Red Death will have to follow.
The Ishtar-Gate
Found 1899 by German archaeologists within the ruins of Babylon, the Ishtar-Gate is reconstructed within the walls of the Pergamon Museum, Berlin. It will be finished in 1914. Babylon was called “the Whore” but also “the Gate of the Gods”
Forbidden Lore: When it is reconstructed, the magic of the Gate will allow to open a gateway to the planes (maybe to the Mists of Ravenloft).