Here is the most exciting thing that will happen in 20 years in bonsai:
Due to the advancement of genetic engineering, we will discover the gene that makes a species adapt to different climate zones. As a result, we will be able to grow genetically enhanced larch, fir, white pine, and spruce, that can thrive in a mediterranean climate. We will also be able to grow Pemphis, and other tropical species, in our cooler climates, and import killer material from Robert Steven.
This, to me, will make growing bonsai incredibly exciting, since one will be able to grow trees irrespective to their native climate.
On the flip side, this discovery will cause unimaginable devastation in our environment: local flora will be destroyed and replaced by these plants with "super-genes", the natural balance will disappear, and ecological devastation will follow. Rightly so, society will blame bonsai for all this, and there will be a bonsai prohibition, similar to the one in 1920 - 1933 in the U.S. Consequently, bonsai prices will skyrocket, and everybody will grow moonshine-bonsai in their back-yards. Inevitably, the mob will get into the bonsai-business, and they will be the main financiers of (secret) bonsai conventions.