Let me ask you to do a semantic analysis of three versions of the statement, the Quranic version and two other versions that look like it, in order to pinpoint how the Quranic version is different. All three contain the following meaning:
"a verse getting abrogated" implies that "a verse that is better or similar will be brought"
but they may have additional connotations that are different. The three versions are:
... نأت بخير منها ... (with سكون tashkeel) ما ننسخ
... نأتي بخير منها ... (with ضمة tashkeel ) ما ننسخ
... إلا ونأتي بخير منها ... (with ضمة tashkeel) ما ننسخ
Here is the analysis of the 3 constructs:
1. The Quranic construct:
... نأت بخير منها ... (with سكون tashkeel) ما ننسخ If we abrogate ... then we bring ...
ما is used here as a conditional article as evidenced by the grammatical state of the two verbs
ننسخ and
نأت which is
مجزوم (
majzoom, with the last letter of the verb 'unmoved'). The full parsing of the verse is given in
this link, and the details of the applicable grammatical rule are
ما أداة شرط جازمة تجزم فعلين: فعل الشرط وفعل الجواب، وتأتي لغير العاقل، مثل: مهما تقرأ يزدك معرفة. مهما اسم شرط جازم مبني في محل مفعول به لأن فعل الشرط تقرأ واقع على معناه، و تقرأ فعل الشرط مجزوم بالسكون والفاعل ضمير مستتر تقديره أنت، ويزدك فعل جواب الشرط مجزوم بالسكون والفاعل ضمير مستتر تقديره هو والكاف ضمير مبني في محل نصب مفعول به
2. The second construct:
... نأتي بخير منها ... (with ضمة tashkeel ) ما ننسخWhat We abrogate ... We bring better or similar to it...
To make this grammatically correct, it should be نأتي بخير منه (masculine) not نأتي بخير منها (feminine). In this case, the first part of the construct is شبه جملة (semi-sentence) functioning grammatically as a noun "what We abrogate or cause to be forgotten" and the last part describes what happens to the first part (namely, We bring better or similar to
it).
If the sentence ends with نأتي بخير منها, then that part is a separate sentence. In other words, the meaning would be, "We do not abrogate a verse or cause to be forgotten. We bring one that is better or similar." That would imply that both verses remain and one is better than the other but the first one is not abrogated.
3. The third construct:
... إلا ونأتي بخير منها ... (with ضمة tashkeel) ما ننسخWe will not abrogate ... except when We bring ...
This is a declarative confinement (أسلوب قصر), implying "only when We bring better or equal that We will abrogate a verse. No exceptions." This construct kicks the negation up a notch
. Here,
ما is used to negate the verb. We can tell using the conjugation of the following verb; it's unchanged. Also, this criterion is mentioned in grammar books,
ما ولا حرفا نفي. وتدخل "ما" عادة على الفعل الماضي، وتدخل "لا" على الفعل المضارع. ولاأثر لهذين الحرفين على إعراب الفعل الذي يليهما
Based on that criteria, the negation in this case (with a present-tense verb) is more likely to use
لا than
ما making the construct
لا ننسخُ ... إلا ونأتي, but
ما has been used for present tense elsewhere in the Quran
Anyway, out of the three expressions, if we make a ranking of how much each expression suggests that the first part (abrogation) would occur (similar to the ranking implied by the "if" articles إذا versus إن versus لو ), I feel that the Quranic construct is in the middle, with construct 2 making abrogation more likely and construct 3 making abrogation less likely.