With Daedelic's recent moves, we probably won't see it here, not sure if it really adds much too.
But still interesting.

G A M E N O T E S
Trash, trash and more trash. Life on the junk planet
Deponia is anything but a vacation pleasure. No wonder that Rufus therefore attempts with one hair-raising plan
after another to escape from this desolated place. When Rufus during one of his attempts to escape meets Goal
and falls in love with her an exciting adventure begins

New features of Deponia - The Complete Journey:

Daedalic has summarized the trilogy about Rufus and Goal to a large, enhanced game, for which all three parts
were revised. Also included are optional audio commentary by writer Jan "Poki" Mueller-Michaelis and
other designers.

The three previously individual adventures are hanged in each other, but retain their intros as part of their
story. The transitions between the individual parts are softer, you can play through in one go. This acts
'Deponia - The Complete Edition' as a big game, there is no need to "change" the games.

New is a Deponia world map. In addition you can select the required chapter once it has been unlocked. All
savegames are compatible with each other - who wants to switch for example from the floating black market to
Kuvaq, "Deponie 1" automatically loads in the background, without additional handles are necessary

The developer commentary offers over 280 minutes narratives of Poki, as well as special guest speakers
from Rufus (Monty Arnold), Goal (Sinikka Compart) and Goon (Gronkh). There are 6 new songs, written and sung
by Poki, as part of the developer commentary as well as bonus materials (mp3 & flac) on the game disc.

A new quest log with countless drawn graphics (Rufus' diagram overview to get to Elysium) gives tips about
pending tasks. 'Deponia 1' has been extended to secret garbage puzzle pieces. In the bonus menu you can unlock
a Rufus capita scrap statue. The technology was also improved, an engine update and bug fixes to improve
performance were carried out.

This sounds great for those who missed the original trilogy.

This reminds me I still have II and III to play...

What's stopping you? Deponia and Goal need your help!

My backlog, of course :)

so its now availible on steam for 4€ until 8 Sep ;) (if you own the trilogy on steam, for each 30%)
Hope gog will add this too

what moves? are Daedalic leaving GOG?

Not that i am aware of.

They split the edna and harvey games into two (which was sold here first as 1 here).
Asking for money at first for a patch on steam to a very bugged Whispered World.
Putting games like Blackguards or Alcatraz on a sale just 1-2 months after their release.

Another bad move by Daedalic. I mean, since in terms of gameplay this doesn't add anythig, they could just gave it for free to those already own the full trilogy. Yet they are asking 5€ for developer's commentary and stuff like this. I bought it on Steam thanks to a friend (because I miss Deponia 3), as I said I don't like Deponia games, but since I've played the first two titles, I want to know how the story will end.

But then, the extra provided here could just be added for free on Gog (and Steam).

And why are those moves prevent Daedalic from putting the game here?

That sounds like an episodic game, such as Tales of Monkey Island or Sam & Max, which are available on GoG (in bundles).

Because they are killing themselve with all the moves they made and perhaps will be making, and with what they did with Edna and Harvey here, i doubt GOG would have been happy with that move too, putting up a higher priced version of Whispered World here (that is $10 more of the original price) for just a patch and some added commentary, and same might go for the sales they did which they didnt do first here, So unless they learned from their past mistakes.
Beside, it's not really a new game here, as Punished_Snake said, gameplay wise there isn't much new atleast.
Since they charge $20 for each episode it's probably even unlikely that it will come here because together it will cost $60 which GOG doesn't do and well they will have to seriously cut down in price then.

I'm curious about the retail, boxed version. From what I can tell, it is only available in Germany. I'd contemplate importing it, but will that release have English dialogue? The commentary will probably only be German, but there are enough other nice bonuses that could justify the effort as long as I can understand the game itself. Anyone know?

I don't know, but I think it's unlikely. I have the retail version of Daedalic's Night of the Rabbit and that one is German language only.

The comments on amazon.de also state that the released version of Deponia: The complete Journey is pretty buggy so far.

I've never really understood Daedalic's business practices. They make some of the most baffling decisions I've ever seen in my life, and yet they seem to still make a good chunk of cash from it, considering they keep pumping out game after game like there's no tomorrow.