Interesting thread OP, I have just turned 40 and I have been thinking about this a lot. The short answer is, no, I don't have a passion for anything. In reality, I did, but for one reason or another, that passion has drained from me...
Throughout my childhood, I was obsessed with computers. That was my hobby. I was pretty good at it too. Then I got an apprenticeship in IT, and now, 23 years later, I'm still doing an IT Support role. It's actually not a bad job all in all, pays OK, not spectacular, but then I have little in the way of responsibility, stress or pressure; although should I be lucky enough to be promoted, the money will change but the job wont really change at all - win/win. However, getting back to the relevant bits of the thread, I have to say, that the job has certainly to some degree killed off my passion for computers. When all you do all day is deal with Windows faults and another broken HP laptop, you kind of lose that passion somewhat!
As a sidenote to that, I was really into gaming as well (not really a surprise, I expect I'm in good company here). However, now, I don't have the time or motivation to play games I used to. The time thing is called being an adult, but the motivation I suspect is a few things: games are much more complicated than they used to be, and computers are too. If I have a half hour time slot, I'm often greeted with an issue I didn't know existed or an update that needs to be done before I can play. There's my half hour gone. Maybe if I had longer than that, I'd simply decide I CBA instead. So yeah, games have lost their fun too.
I was really into cars, sports cars, hot hatches. However, I always got into debt for the car and then couldn't afford to run it properly. I had a string of excellent cars (MR2s, Z4 Coupes, 350Zs, Clio 172s, Integras, etc etc) but I found that when I was getting more and more into debt it was robbing the joy out of ownership. Now I moved close to the city centre and don't have a car. I do miss it, but I don't miss the bills.
I am also into music and hifi. Only I realised the hifi thing is really a waste of time and money once up to a certain level. I found that I was listening to the gear more than the music. This is the wrong away around. Now I have a system that is 'good enough' and enjoy the music more... WHEN I get to listen, which is less and less now. So I find myself on headphones a lot or listening at work in the build room on a pair of £10 PC speakers. Ho hum...
I used to keep tropical fish. Tank burst in the middle of the night. Now the mrs doesn't want another tank in the house. Another hobby gone.
Exercise - I'm into weights, but I don't love it. I've made OK progress. Problem is I like a drink, so I don't fully realise the (aethetic) benefits.
Oh yeah, did I mention I like a drink. And socialising, is that really a hobby?!
So yeah... I have no passions left in life. I feel like this needs to change...