It really depends on what you want to do. We hire folks from dev backgrounds all the time and many stick around and enjoy it. If you get pushed into some corporate app sec role where you aren't doing interesting problem solving, I do not recommend it. If you get to really dig into security problems and challenges using engineering and technical skills you have acquired, yes, it is still fun. You get to take apart other people's puzzles (apps/code) and there are tons of opportunities for automation, scripting, writing tools, etc. It is an awesome field to grow in when you have a lot of hard CS and development skills and can apply them meaningfully. That makes things pretty narrow in terms of roles out there that check all of the boxes I mentioned, but, yes, it is still interesting and fun. Look at all the cool things people have done with fuzzing over the last 5-10 years, starting with AFL which really changed the game. Now people do fuzzing with VMs (qemu) etc. Just a ton of really cool stuff that a solid C/C++ dev can really dig into and play with :)
I think the trick to staying happy in cyber security is to chase down niche fields in technology. Your work won't be perceived as sexy by the broader community since you're not tracking north korea, but the trade off is that you will have fun and not have to brush shoulders with so many egos. So what's green these days? That's for you to decide, but one area I think is interesting is smart contract security on blockchains. Lots of folks are pouring into that space.