I wish I had bought one years ago at RDNA, but does anyone know if the Tera dome still works in Poser, or if Renderosity is planning an update on the system???

If you only use Firefly, it works perfectly fine. I have both TerraDome and TerraDome2. Some of the textures work in Superfly as well; it's been a while since I used it though.

Here, quick and dirty Superfly render of TerraDome2, out of box preset morph and textures:

The same here.  Despite its elaborate shader work, it still works in P12.  It's amazing that the node connections still remain intact through the P11/P12 iterations.  You can find Terradome and expansion packs at DAZ and they are running a 60% sale on all the modules.

Is not the base Dome included in Poser 12 content pack ?

I think that the Dome was already included in Poser2010's content, but you don't need it if you use the background node, especially if you change the second parameter of the location of the Mapping node: 0, 0.2, 0 = 20% higher for all the scene, except the HDR bitmap.

Terradome was never included in Poser, at the time, it was an exclusive bundle sold at RDNA.  As I mentioned, if you still want to purchase the base and its modules at DAZ3D.  And now looking at their product page, the 60% holiday sale is over.  Most of the bundles and modules were below $20.

Looks like I was wrong because I wasn't as organized with my runtimes as I am, sorry for the confusion.
Just be careful: only Terradome 1&2 are compatible with Poser, the V3 will need to be converted.

There was a v3???

V3 I believe didn't come out until after RDNA moved to Daz and was the DS compatible one.

Ah, well, never even saw that one.

 I Do know there is a TD3, and I also know that while DAZ holds the rights to Terra Dome for DS, that doesn't stop Renderosity from making a comparable version for Poser. Or, The creators of Terra Dome could make a version for Poser.

You seem to misunderstand, there is a Poser version and it is available in the DAZ store.  Check their webpage.  Poser is clearly mentioned under 'Compatible Software".  There is no need to approach the creators on this issue, they sold the rights to DAZ3D and you can purchase a Poser working version and all the associated modules.  And as I mentioned above, you missed your opportunity to save 60% on each bundle and module over the holidays.

TerraDome 1 and 2 works perfectly fine in Poser. As hborre mentioned, v3 seems to be DAZ only, but that doesn't mean 1 and 2 are obsolete since they are for a different software. TD2 even has a TerraLuna extension that helps you to make space renders.

ETA: I looked at TD3--it seems almost 100% a rework of what TD and TD2 offers to Poser users.

(29) TerraDome 2: The Badlands - YouTube

(29) TerraDome 3 For Daz Studio Iray - Overview - YouTube

Here are the promo videos that were made for each version.  I have both Terradome 1 and 2 and most if not all the extras. Really sad when RDNA shutdown and this system got froze in time. Personally TD2 has the better video in that it makes you want to do something with it.  Especially the morph terrain as the camera flys byvs here what the sliders do. 

I really need to get inside this bundle and give it the Superfly Cycles treatment.

Terradome is still very useful. Maybe we can ask the original creator to come back to poser and make something similar completely for poser 11/12

MortemVetus has a number of expansion packs for terradome2 here at Rendo, some have been sold elsewhere but a couple are new.

A quick P12 Superfly rendering converting materials to PhysicalSurface PBR, eliminating the IBL and specular lights, and converting the point light to infinite Blackbody sunlight.  The skydome could use the HDR touch, perhaps converting the JPG to HDR might do the trick but that requires experimentation.