This seems unlikely...even if the original core developers stopped doing anything with bitcoin others would take their place simply due to bitcoin's popularity and the availability of the source code. Even if the bitcoin popularity and development declined significantly it would not really die because the blockchain and ability to make transactions would still be there as long as we have the Internet. The only thing that would happen in such a case is that there would be fewer transactions taking place and the value of each BTC may decrease as demand decreases.
in my opinion the death of bitcoin will occur when the people around the globe stop accepting bitcoin as their regular and legal currency, or the other cause is the availability if there is no bitcoin available in the market, what will people buy? But I am sure it will never happen because lots of people are there in this market and they will never let bitcoin die because of the benefits they receive.