I see Sony, rather than Warners, appears to be the designated buyer-outer of MGM. To those of us mostly concerned with what happens to the classic film library, this isn't a good sign; Sony/Columbia used to bring out some good special editions of movies like Mr. Smith Goes to Washington and His Girl Friday, but in the last few years they've almost completely stopped bringing out DVDs of older films (and the ones they do bring out are usually shorn of extras and hideously overpriced, like their DVD of The Awful Truth). They're a little better when it comes to older TV shows, but they bring shows like All in the Family out with no extras and shabby-looking packaging. MGM's DVD department was erratic, but they did release a lot of older movies, including some pretty obscure titles. The good news is that they've already released most of the best titles they have in their catalogue -- like all of the movies Billy Wilder made for United Artists.
Because, of course, MGM doesn't own MGM movies, at least not MGM movies made prior to the late '80s or some such time. MGM sold off its catalogue to Ted Turner, who also owned the pre-1948 catalogue of Warner Brothers movies and cartoons; when he merged with Warner Brothers, they wound up with the biggest catalogue of old films (which, fortunately, they currently seem to be handling well, DVD-wise). And of course, MCA/Universal owns all Paramount movies made prior to the late '40s. The shifting ownership of old movies has been going on for decades, of course -- a function of the short-sightedness of studios like WB, whose desperate executives didn't understand that there was more money to be made by holding onto their catalogue than by selling it off.
Most of the time these changes of ownership don't mean much, but on occasion they can change the way movies are perceived by the public; for example, the Warner Brothers cartoons: WB sold off all the color cartoons they made prior to 1948, only to realize -- too late -- that there was an enormous TV market for those cartoons. So their subsequent TV repackagings (The Bugs Bunny Show and such) used only cartoons made in 1948 or later, while local stations bought packages of pre-1948 WB cartoons -- creating the perception that these were two separate "eras" of cartoons, and changing the way the characters were perceived (the angry, greedy Daffy Duck became, for some time, the "definitive" version in large part because most of the cartoons in the post-1948 package showed him that way). Another possible example is the way movies from one studio are now sometimes packaged with movies from another studio; when WB brings out a "film noir" collection with a lot of RKO movies plus an MGM film (The Asphalt Jungle) it tends to create the impression that MGM was part of the hip, gritty film noir scene, when it wasn't really. I wonder if it'll get harder to view MGM or WB's output as having a particular style when more and more MGM movies are coming out on the WB label? The MGM movies still have Leo the Lion roaring on DVD, of course; I'm just saying that part of what gives a studio an identity, a style, is that its movies are kept separate from other studio's movies; throw them all into the same mix, put them in boxed sets with movies from other studios, and they may start to blur together in the public mind, so that the stylistic difference between '40s MGM and '40s Warner Brothers movies may not be as clear now as it used to be. But I admit that's just speculation on my part.