For many decades, Mexico-USA matches in Azteca have only occurred for WC Qualifiers (WCQ), where Mexico has sole discretion on the venue. Similarly during this timeframe, USA-Mexico WCQs have been held, to my memory, only in Columbus where the USA has sole discretion on the venue. Recent Mexico-USA friendlies are relatively rare and when they do occur they have been in the USA, at large venues that are mutually agreed on. Mexico-USA also play in Gold Cup matches - held in similar large venues in the USA.

For the 2026 WC, Mexico, USA & Canada qualify as hosts, so do not have to play in the CONCACAF qualifying tournament. Meaning, no USA-Mexico matches in Azteca in the next two years.

The format for CONCACAF WC qualifying for 2030 has not been determined, but CONCACAF will have 6 or more direct qualifiers plus playoff qualifiers from 2030 and beyond - so it makes no sense to continue the traditional "Hex", the final double round robin of 6 teams. And to my mind, the only format that makes sense is UEFA style format - 3 seeded groups with the top 2 teams from each group qualifying for the WC. USA and Mexico would surely be in the top pot for seeding and thus they would be drawn in different groups. Meaning that if I am right, no USA-Mexico WCQ matches in Azteca for the foreseeable future.

The only way I see Mexico-USA matches in Azteca is if:
1) CONCACAF decides on COMEBOL-type WCQ system (double round robin with 10 teams, 18 matches/team over 3 years), but there isn't room in the international calendar for sub-qualifiers, so it is unclear how they would pick the 10 teams and conform to the FIFA requirement that every national member has an opportunity to qualify for a WC (CONCACAF has 41 members I believe).
2) Mexico starts hosting the Gold Cup. The economic incentive to keep USA as the host is immense. Moreover, I understand that there is a move to reduce the frequency of the Gold Cup to every 4 years (currently every 2 years) as the Gold Cup really does not provide the competitive quality that the USA (and Mexico) need, especially with CONCACAF nations league matches thrown in as well. USA (and Mexico) would prefer to reduce their CONCACAF commitments in order to play in every Copa America tournament (COMEBOL) and/or schedule higher quality friendlies.
3) USA agrees to play friendlies at Azteca - which is highly unlikely for many reasons.