From what I've read lately, they are very much alive. I read in the News that they were back in Afghanistan again now. They're still around. ISIS has pretty much stolen the news headlines lately and you don't hear much about them anymore.
Was al-Qaida defeated? How come we don't here about them in news broadcasts any more?
Nope.
Here's a dirty little secret few in government will admit to:
NO terrorist organization can be defeated by military force. They just divide up into smaller cells, so it isn't logistically feasible to use a military against them.
It's the nature of news providers that they present the most sensational news. Recently Al Qaeda haven't been making as much noise as ISIS so they're not getting as much coverage. Don't worry, we'll hear plenty after their next atrocity.
Do understand that newspapers and TV news sources play on the emotions and outrage of their audience and the more sensational the story the more products their advertisers can sell. They're less interested in truth and balanced reporting than sensation.
Fortunately some sources are more reliable than others and, with care, you can keep abreast of what's happening.