Sorting out the Sabatier knives might turn out to be someone's (almost) full time effort.
The Sabatier name goes back to the early 19th century in Thiers. There were at least two separate cutlery makers with that name, Jean Sabatier of Le Moutier (Lower Town) and Phillippe Sabatier of Bellevue (Upper Town) in the post-Napoleonic period in Thiers. Descendants of Phillippe Sabatier are still associated with the firm he founded (Sabatier, Aine & Perrier), making knives today offered under the "Sabatier K" brand.
However, after Phillippe Sabatier and Jean Sabatier, the number of separate french cutlery makers offering "Sabatier" knives mushroomed. The Wikipedia page on "Sabatier" knives shows 30 different brand names associated with the Sabatier name. By no means were most, or even many of the French Sabatiers made by descendants of the two Sabatiers of the early 19th century.
At this point intime (2014), as noted above, "Sabatier" branded knives have been sold that were even made in China!
Lion Sabatier has been one of the "historic" Sabatier lines, and the current owner of the brand, Rousselon Freres, acquired the Lion Sabatier rights in 1991.
So, yes, Lion Sabatier is considered a legitimate Sabatier brand.
There's a different twist to this story. That is whether the knife is made from carbon steel or from stainless steel. Like many industries, the kitchen cutlery industry to a large degree shifted after World War II from carbon steel knives to stainless steel knives. The newer stainless steel blades could be polished up much more than the old carbon steel blades and were more resistant to corrosion and rust.
However, the newer stainless steel knives simply could not compare to the older fashioned carbon steel knives in the ease of taking and holding an edge.
Some of the current Sabatier cutlery makers (such as Thiers Issard and Sabatier K) make both stainless steel and carbon steel blades. As for Lion Sabatier, since that brand does not seem to be imported into the United States in any significant numbers, I do not know which type of steels are used or offered.
Today, if I was looking for a new Sabatier knife, I would look to see if it was made from stainless steel or from carbon steel. If stainless steel or Inox, I would probably pass it by. If carbon steel, I would get excited.