You forget the basics of the theory of special relativity.  Time is not only distorted by speed but also by gravity.  A number of black holes have been discovered that may well be beyond our ability to travel to now but not at some time in the future.

In any case a “time traveller” would not have to travel anything like a 100 years nor even 1 year if travelling at or near the speed of light in order to “jump” 100 years of Earth time.