Just so you know that you and I are in the same camp on this one, I've already purchased a life insurance policy on DJ Trump, so I'll split my winnings with you when I receive the payout check in the mail!
What you speak of is of valid concern, though a past President like Reagan and Reaganomics for example, cannot be compared to Trump and Trumpism. Both are two birds of an entirely different feather and to try and compare both political eras as being co-related in some fashion with each other as some here in this thread are attempting to do, is a complete misunderstanding of the concept of MAGA and Trumpism.
When Trump bites the dust in the foreseeable future by some natural cause, such as a direct hit from a lightning strike or the collapsing of a concrete bridge onto his personal car driven by his youngest son "Lurch Trump" while out on a father and son bonding expedition on a Sunday afternoon, WHO will be the lucky one who will actually take over the MAGA movement the next day?
Technically speaking, it would be JD Vance who of course is Trump's VP, assuming that Vance wasn't with The Donald and son Lurch on that Sunday drive in the country. JD Vance though Republican, is not a representative figure that anyone will connect with the MAGA movement. JD Vance therefore, cannot carry the MAGA torch as Trump's equal.
The thing is, MAGA is not a Republican movement, MAGA is an extreme right-wing Trump movement. MAGA represent the extreme right, whereas Republicanism in America represents the 'center-right'.
MAGA has a mascot who's name is Donald J. Trump and Americans from both the right and left sides, identify with MAGA as being Trump and Trump as being MAGA, meaning that both are seen together as one entity at all times and never as separate entities unto each other.
What this means is, when Trump dies, the concept of MAGA dies along with him because MAGA cannot and will not be represented by some alternative political figure like JD Vance for example.
Remember what happened to the Charlie Kirk saga?
As soon as Charlie died, the Charlie Kirk movement and it's political Foundation collapsed completely within 30 days of his death and nobody talks about good `ol Charlie anymore.
The same thing will happen with Trump, Trumpism and MAGA when Trump exits his lifetime, stage left. When Trump dies, the MAGA movement will end immediately until a new cult name and political figurehead is created by the extreme-right, who will then attempt to push the old MAGA agenda but will present it as a different color than the old MAGA use to be. In other words, a re-branding of MAGA will likely occur and a new mascot will be assigned the role of Parade Master to that new branding.
The likelihood of that happening however, will be slim to nil, because the only reason that MAGA worked so well in the first place is because of Trump himself, not because of what MAGA represented as a stand-alone right-wing cult following.
Nazism in Germany in the 1930's didn't become popular because of Nazism itself, it became popular because Hitler, an unknown man who hid in the political shadows, piggybacked his agenda on Mussolini's intense popularity among the Italian crowd in Italy.
When Hitler and Mussolini then took Hitler's show on the road together, Hitler became instantly popular among the Mussolini followers in Italy and German Nazism began to flourish across Central Europe because of Mussolini's popularity, not Hitler's! The same thing will happen with MAGA. Trump and MAGA are like Mussolini and Nazism. Trump's popularity and Mussolini's popularity is what carried the day in both cases.