The Neanderthals didn't exactly go extinct. The genes in our own DNA show that while they disappeared as a species, they were assimilated and absorbed into the neolithic Homo Sapiens populations of Eurasia. Possibly their largest long-term contribution was a particular gene relating to our immune systems, and since these were concentrated in the European end of the land-mass, and to a lesser degree on the Asian end, it may well have played a role in the more disastrous elements of European contact with the Western hemisphere in regards to disease.
And their stone tools, the flaking geometry and construction methods were often more intricate than some comparable Homo Sapiens tools. The flint knapping techniques were more complex. The "Smarter" Homo Sapiens may have figured out easier ways to do some things, and passed this along, but the skill required in some Neanderthal tools was greater. Judging by tools alone, they may not have been as "smart" as Homo Sapiens, but only for doing it "the hard way".
Other theories that believed Neanderthals didn't have "Religion", or "Art", have been proven wrong, with finding archaeological indications of funerary rites/offerings, and jewelry/decorations...
The complex tools, the decorations and signs of other complex cultural activities makes the last idea that they didn't have a similar language faculty as Homo Sapiens to convey all this information to each other difficult to believe too.
Meh.. I have a suspicion that the results might actually be underwhelming beyond physical appearance. Especially with no real way to socialize this prospective Neanderthal child in Neanderthal culture. Even then, I have to ask if it would be all that different, considering the genetic evidence is there that the populations were similar enough to interbreed as they did. I suppose one could theorize that it was all by force with no basis in cultural compatibility, with no real way to prove or disprove that archaeologically or paleologically, but it seems unlikely to me.
Considering that it's possible to socialize a gorilla into keeping a kitten as a pet, expressing it's grief when it died, and having the vocabulary (In American Sign Language) of a kindergartner, I don't think that if these researchers actually pull it off, they'll find something all that groundbreaking, other than the actual attempt and the birth of a viable Neanderthal child itself.
