COD could potentially be dying now, with "death" as you put it coming for the release after Black Ops II. Or, Black Ops II could re-steady the ship from the rolling seas of the last 2-3 years.
COD4:MW has to be seen as a resurrection or birth of sorts and COD:WAW did nothing but confirm the promise that this could be a great series.
COD:MW2 could be seen as the start of a decline in terms of ideas and cash-ins, however the real problems came afterwards and lie with lag (connectivity, matchmaking, lag compensation, poor porting, etc.). This was a real shock to fans of the genre when it arrived alongside COD:BOps. The game itself (innovation, balancing, design, etc.) stormed COD back up from the lull of MW2's lack of uniqueness but a whole new b***tard beast was unleashed.
When these game-breaking issues were not addressed adequately in COD:MW3 (in fact, it's even worse) that the game was even less imaginative and balanced than it's forebear, MW2 didn't really matter. That MW3's maps and spawns were atrocious is in pale insignifigance alongside the fact that not only can you be insta-killed by intended game mechanics but along by poor game design and shockingly awful lag. Many deaths are hard to figure until the killcam plays. This is no COD of mine, or ours.
If Treyarch pull out a gem for COD:BO2 (and I know they will plan to) then all that remains is the lag question.
The answer to this question will answer your question. Lag largely resolved and COD will live on and thrive, even at next gen time. If the lag is gamebreaking for the third game in-a-row, irreparable damage will have been done and COD's days, like those of "Soap" McTavish and shower soap will be numbered.