As far as I understand it, Sony doesn't own BluRay. So by using it to beat HD-DVD Sony won a battle for the companies that do own it. With no big reward for their efforts that I can see.
No one company owns Blu-ray. The format is owned and licensed by the Blu-ray Disc Association (BDA) of which Sony is a member (and in fact a Board member). The license fees paid to the BDA are split several ways, including to Sony. This means that Sony get some money out of every single Blu-ray player sold, every Blu-ray drive sold, and every Blu-ray disc sold.
I was going to say "yes, definitely," but then I realized that I've only ever played a handful of Blurays on my PS3, and most of the movies I watch I stream through a service, either through my PS3 or other devices.
In fact, what Sony did right was allow for us to use external HDDs rather easily, rather than buying Sony brand HDDs at a ridiculous price (ahem).
Moving forward, I think the focus should be on online services/streaming, which should probably include a massive internal HDD, but as long as we can still use our own external devices, and if the PS4 can quickly stream such data, then it should be fine anyway.
"Only good thing about Sephy was his music; Only thing he ever did was throw his mom at you and stab a flowergirl." - BattleJesus
Considering the initial cost of it to be in the PS3 to begin with and now considering it hasn't dethroned DVD as the main medium people buy their movies on. Plus the advent of streaming services eating at their market from what I've read.
Is it nice to have? Yes. I know I wouldn't own a BR player otherwise. But even then I buy most of my titles on DVD unless it's something really worth it to me like Avengers was.
Was it necessary for this generation? I don't think so. 360 got on fine without it. This coming generation would have been the better starting point IMHO. But whatever, it doesn't really matter.
Considering the initial cost of it to be in the PS3 to begin with and now considering it hasn't dethroned DVD as the main medium people buy their movies on.
I don't think the BDA really expected Blu-ray to take over from DVD in the same way that DVD took over from VHS. However, Blu-ray has captured a significant portion of the home video market, probably including the most profitable parts of it, and it would have provided an overall sales boost to that market due to repeat sales and increased levels of consumer interest. It'll probably become the most popular physical disc format over the next few years.
Plus the advent of streaming services eating at their market from what I've read.
I suspect that they're eating more at DVD than at Blu-ray (right now, at least).