とは限(かぎ)らない is regularly used to convey the meaning of ‘(A) is not necessarily so’, or ‘there is no guarantee that (A)’. This expression utilizes the 格助詞(かくじょし) (case marking particle) と in its use for highlighting 結果(けっか) ‘results’, the 副助詞(ふくじょし) (adverbial particle) は, and the negated form of the う - Verb 限(かぎ)る ‘to limit’.
This structure may be used with verbs,
い-Adjectives,
な-Adjectives, or nouns. However,
だ will be required after
な-Adjectives and nouns.
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日本(にほん)に2年(ねん)間(かん)住(す)んでいるからといって、日本語(にほんご)を話(はな)せるとは限(かぎ)らない。
It is not limited to a person being able to speak Japanese just because they have lived in Japan for 2 years.
日(ひ)が出(で)てても暖(あたた)かいとは限(かぎ)らない。
Just because the sun is out, doesn't necessarily mean that it is warm.
田舎(いなか)でも静(しず)かだとは限(かぎ)らない。
A place being rural doesn't necessarily mean that it is quiet.
社長(しゃちょう)だからといって乗(の)っている車(くるま)が高級車(こうきゅうしゃ)だとは限(かぎ)らない。
It is not limited to him driving a luxury car, just because he is the CEO.
限(かぎ)らない literally means ‘to not be bound’, or ‘to not be limited’. Therefore, despite と highlighting a result, that result is then being clarified as ‘not the only possibility’.