Meh. I've seen plenty of games where a few "leads" left and the game came out fine, and plenty where none left and the game came out weak. I'll stay in 'cautiously optimistic' mode.
I don't think Bioware is in a slow, downward spiral. It seems more like they jumped down a few pegs when EA forced the quick release of DA2 and have been hanging out at around that level ever since.
I consider myself to be "cautiously optimistic" as well, or maybe it's "blind optimism"; I just can't completely write off one of my favorite RPG developers. It's the "EA Effect" and influence that bothers me, a corporation that pushes that "profit above all else" mentality, and often disregards the single player RPG game with a deep story that Bioware is known for.
I understand the need to make a profit, the gaming industry has become increasingly brutal over the past few years with rising production costs and the need to sell a certain amount of "game units" just to break even. Which is even harder on the smaller game developers that don't have corporate funding.
It just feels to me that the seemingly constant departure of creative talent of Bioware reveals a conflict of interest between Bioware & EA. And as you stated, creative leads leaving a studio doesn't
always mean that a game will be bad, but too many have left Bioware recently for me to feel comfortable.
While ME Legendary and the ME4 teaser gave me some optimism, both ME4 & DA4 have "supposedly" been in development for years, and we've yet to see any actual gameplay footage or even images. That, to me, doesn't bode well. But I will maintain a certain level of optimism, blind or not, that maybe these games series will continue.