What we do not yet have, and what Rothenberg is calling for, is a software program that will allow us to run present-day programs on future, unbuilt, and undesigned machines. That is a challenge. Predictably, there are quite a few who disagree with the theory of emulation, and if they agree with the theory, they nonetheless find it unfeasible. And many of the objections to emulation mirror those leveled against migration. Let me summarize one computer systems scientist's list of the major impediments to the development of a reliable emulation strategy.
Emulation is actually quite hard both for hardware and for software.
Both hardware and software interpreters are very seldom specified completely, and the more complex the system, the harder the problem becomes. In case you had not noticed, systems are growing more complex, not less. Even MIME encapsulations of simple e-mails will produce radically different displays on various computers. The only way to ensure that one has captured all the relevant features of an environment is to copy it entirely technically impractical and from the licensing and intellectual property viewpoint, ludicrous. We cannot anticipate all the digital forms and formats that will evolve.