I am the Spock and T'Pol of opinions on this entertainment-spanning debate, forever of two minds, two worlds.
On the one hand I absolutely agree. Fully-realized, totally-told stories are a thing of beauty. If I can begin a thing, reach the middle of said thing, arrive at the end of said thing, and feel completely whole... that's a good, good feeling. Too frequently in modern media so much is perpetually held back, all the better to convince newly-built audiences that the best is yet to come. "2018 will be so good for Marvel." "Just wait until the fifth Dragon Age game; that's where it'll be really crazy."
On the other hand I can't get enough of shared universes. I used the Vulcan analogy because, growing up, Star Trek was my shared universe. There was a synergy in 90s Trek that many younger consumers would think was invented by Kevin Feige. I ate it all up. And for more centralized, focused IPs, such as Mass Effect, I ate up all the speculation between chapters. Hungrily. Fandom guessing games are one of the best aspects of entertainment and the ever-present feeling that a given franchise is far from truly over is a comfort. There are a great many things on the market that I do not like, so it's a joy knowing the things I do like are ongoing, ever-evolving.
But those evolutions can become devolutions. And that ongoing nature can prove detrimental as hell to each piece of the tapestry. And the thought that I won't be able to experience a full video game trilogy all at once, in all its glory, through all its triumphs to all its failures, for something like six or seven years past its initial unveiling... well, that's a highly bittersweet sensation. Who's to say I'll be alive then? Who's to say BioWare won't go under, somehow? Indeed, who is to say the original creative vision behind such a venture will be remotely in-line with what we see by the third entry? No one. No one knows.
For all that cautionary philosophy, however, still, I love it. And while I'm doubtful the new game is being planned as a trilogy in the same vein as Shepard's saga, I hope it feels like one anyway, when all is said and done. Because I want to look back and feel like I truly knew these characters, this setting. I watched them mature, transform. And I haven't seen a single video game capable of that degree of narrative fullness since the halcyon days of Square.