Tell someone from 1909 that within several decades hundreds of millions of people would fly every year.
Technology has a way of rendering proclamations like that into quaint notions within an amazingly short period of time. All it takes is for one unforeseen development to make our wildest imaginings look tame.
Going out on a limb, I'll predict this. IEF fusion is real and will be developed within the next 10 years. Lifters powered by such reactors will be built within 30 years and will be able to put well over 1000 tons into orbit at a time. Thanks to genetic engineering, unicorns, griffons, and dragons will exist within 50 years. The first bipedal humanoid robot workers will be avaliable by 2020. The first manned space colony to top 100,000 inhabitants will exist by 2100. Hopefully I'll be around to see all of it.