〜ないとも限らない
Formation
Meaning
Used to express that there is a possibility that something might happen, or that it is not absolutely certain that it will not. It suggests a potential outcome or possibility, even if it seems unlikely.
Note
A double-negative expression ('not not limited to') that effectively means 'something might happen.' It is often used to express concern about a potential negative outcome or to suggest a possibility that shouldn't be overlooked. While 'kamoshirenai' (might) is neutral, 'nai to mo kagiranai' often carries a nuance of 'it's possible that (something bad) will happen, so be careful.'
Examples
一生懸命準備しても、失敗しないとも限りません。
Even if you prepare as hard as you can, it's not impossible that you might fail.
この薬も、効かないとも限らないから、飲んでみよう。
Since it's not impossible that this medicine might work, let's try taking it.
雨が降らないとも限らないから、傘を持って行こう。
Since it's not impossible that it might rain, let's take an umbrella.
明日、彼に会えないとも限らない。
It's not impossible that I might be able to meet him tomorrow.
彼の言っていることが、嘘ではないとも限らない。
It's not impossible that what he is saying is a lie.
犯人は、あの人ではないとも限らない。
It's not impossible that that person is the culprit.