It is simply evaluating what the term should be prospectively in a way that we presume this Court should presume is legitimate under the First Amendment. When it legislates retrospectively, it is, in effect, looking at particular authors and estates of authors who are before Congress asking for this extension, and it's choosing between these particular authors and the public at large.
The estates of the authors being referred to are those who died from natural illnesses only.
We do not know how the authors who dies and left estates became dead - it could be natural illnesses, or other causes, we do not know from the context so the statement is neither definitely correct nor definitely incorrect.
( z1 estate :poss ( z2 person :ARG0-of ( z3 author ) :ARG1-of ( z4 refer ) ) :domain ( z5 person :ARG1-of ( z6 die :ARG1-of ( z7 cause :ARG0 ( z8 ill :ARG1-of ( z9 natural ) :mod ( z10 only ) ) ) ) ) )