Do you think this name is acceptable for my future child?

It may not be a problem for her among her own friends because they may not have any idea who Portia de Rossi is. But, yes, older people will probably make that connection. Ellen DeGeneres is a highly visible lesbian (a lightning rod for conservatives who are opposed to homosexuality) and Portia de Rossi has a successful career of her own. It's hard to say whether the name Portia in addition to the lesbian connection would be a problem for your daughter, just as it's hard to say whether the social climate will be different when your daughter is growing up. Teens and young adults today are far more accepting of gays/lesbians than older generations are, so it may be a non-issue by the time your daughter is a teen.