You, and others, are reading current conjecture. The details are not know yet, as far as I can tell. Permanent Residents may be able to buy into IMSS, or whatever the new system will be called. If you really must have medical insurance to cover your routine office visits and medications, Mexico may not be a good choice for you.
There are many rumors about public healthcare no longer being offered to foreigners in Mexico, yet I have not been able to confirm this and I have been trying. I heard from one individual who claims that he was denied coverage and that he was told that it was no longer being offered to those with Residente Permanente status. However they there were a few questions that were unanswered in his account included specifically when this denial occurred. So, I am awaiting confirmation. Although it might seem logical given the current political situation in both Mexico and the US, I await more reliable information. If you have applied and been rejected or turned away from applying, please share the details including when and where this happened. Thank you. Meanwhile, here is an article I wrote recently on this subject. https://www.expatsinmexico.com/the-future-of-the-seguro-popular-program-for-expats/
We renewed our IMSS coverage, which we have had for maybe 7 years now, in early March, Interestingly, we received our Mexican citizenship last fall, but I do not believe that we needed to show those credentials to renew our IMSS ins. If that is a new requirement then someone upstairs really has our backs :-)
I remember when we first received our RP status, INM sent along a 'welcome' letter that enumerated all the benefits we were entitled to as residents of Mexico - which included healthcare coverage, educational opportunities etc. We never received a follow-up letter rescinding any of those benefits...
Yes to dual citizenship -- unless the country giving you citizenship requires you to renounce your US citizenship. The US doesn't require you to do so. I know people with both US and Mexican citizenship.
My real estate broker's husband just became a Mexican citizen. For him, he said the process was mostly about paying fees. I guess little to no having to learn about the country and memorizing some historical documents. He said after 60yrs old just paperwork and pesos. I guess there are some benefits, though. I don't have time to even think about it as I am so new I am still learning where to pay my water bill and remembering to without a notice!
I think the path to Mexican citizenship was undergoing changes right about the time we were living it. Unlike the INM experience, where we pretty much had all the documents we needed already with us in Mexico, for SRE we needed to collect stuff from the US - and some states don't make that super easy. For example, we needed apostalized birth certificates. We had to make at least two trips into Mexico City. Once to get our federal 'good behavior' letters and another to visit the US Embassy so the notary could help my wife attest that she is who she says she is even though it is her parents name on her birth certificate and not my last name :-)
True - after 60 there is no testing of your knowledge of Mexican history BUT, for us anyway, there is now a rather challenging written Spanish competency exam. I'm not going to cheapen anyone else's experience by elaborating further, but in some ways a historical quiz might have been easier. Both my wife (who has lived in 3 Spanish speaking countries and collected millions of frequent flyer miles doing business in Mexico and Latin America) and I failed miserably the first time. That requires something like 3 weeks before you can re-take the test.
And every time a certain somebody in the US opened his mouth and we had not yet been approved we felt some stress.