It's fine if you're in a one-to-one meeting with your boss.
If you're in a team meeting with colleagues, it depends on the context - if change and new challenges are on the agenda it would be appropriate, but if it's a routine progress meeting then it's probably not the right forum for a discussion about job security.
If you are really worried about job security, you should ask your boss to add it to the agenda of the next relevant team meeting and/or ask if you can have a one-to-discussion about it.