If a language was infinitely fast, then any sequence or computation could be executed nearly instantaneously (1 Planck time unit?). That means no more offloading long-running tasks to separate threads, waiting for threads to complete, or even spawning a pool of threads to work in parallel. If a computation is near-instantaneous, then any number of them can be executed and still complete near-instantaneously!
Inter-process communication between systems would still exist, but with computations competing near-instantaneously there would be no need to synchronize them. We get to assume that any computation from either system involved in IPC will finish before the next one begins.
This will really make life easier. When can I have this new language??