Not to do with landscape construction, but heres one of mine.
Engineered plants. A lot of stuff going on these days with developing such things as 'dwarf' plants that never need pruning, low growing grass that doesn't need mowing, or even plants that are disease/pest free. Maybe a good topic.
Another off my head would be new technologies. New equipment, new computers, new ways of communications. With all the new equipment out there, the way things use to be done in our industry are now obsolete. In order to stay competitive, a contractor has to be on top of these things anymore. For instance, internet and lawnsite! Look at how valuable of a tool this! Imagine if every contractor in the country new about this. A Masive amount of information would be shared then. Contractors who didn't come here would be missing the boat then, and wondering how 'xyz' contracting down the street all of a sudden took away all his business.
The gross amount of information now available to contractors is just incredible. The problem is, finding it, understading it, and applying it to their business. May make a interesting topic.
steveair