I find it strange that the OP really wonders why people are skeptical about ME:4
ME:3 was an insult of the magnitude of Indiana Jones 4 or any of the starwars prequels and I agree with many here that the ending needs to be addressed in a meaningful/ logical way .
And if you were to inquire further then yes I would say that I am distrustful of Bioware /EA.
Looking at their game mechanics it hasn't changed from KOTOR 1 and imo it has gotten worse , companions are all love interests and if you do not engage them they somehow are incapable of doing their job which is totally improbable and doesn't invoke believe-ability which is always the key point of a good story.
From an overall perspective I am beginning to see some patterns:
Dragon Age Origins is a game I enjoyed playing, I have never taken a good look at Dragon Age 2 but am not hearing things that make me want to play, but I was looking to buy Dragon Age 3 and because the aforementioned loss of trust I looked at a YT video of 5-10 minutes of gameplay and it looked just like an MMO with a lot of the pointless fetch quests that accompany it.
Mass Effect 1 was a game which fully engaged me and although it had its fair share of bugs too, it never broke the experience for me, ME2 looked better and some gameplay mechanics were refined but all the companion characters had daddy issues and the whole game felt kind of "off" to me but as I knew that ME3 was coming I hoped that it was just a calm before the storm kind of thing, when I finished ME3 I was disgusted not only about the ludicrous ending but the entire ramp up to it ( from the day 1 DLC to the linear character and choices made in ME1 and 2 are rendered pointless unless you like to read results in an email from teh terminal)
KOTOR 1 was a great game with a good plot, KOTOR 2 ( I know Obsidian made it) was a bit less but nonetheless worthwhile and I was actually awaiting KOTOR 3 when they released SW:TOR... a story based MMO... yeah right.
Now I understand it's all about money, but I don't see why making games less and less with each release and not innovate gameplay wise or taking an occasional risk is helping profits ( in the long run it will decline I suspect because you are eroding consumer trust)