If my Dad remarries, is his new spouse automatically his new beneficiary?

My Dad is getting remarried soon. I have no problems with his fiancee. I have been the beneficiary of his 401k and life insurance for years since he and my Mom divorced. He knows I would pay off his bills first then save the rest for my kids. I am curious if his new wife would replace me automatically as beneficiary? I don't think she should be left out, but I would hate for her to say she'd be fair and then run off to Vegas and blow the money, ya know? I'm just worried that if something were to happen, she may not be the nice person she appears to be.