This is all going to change so much over the next 5 years. I would not worry about anything just yet. Just be respectful and follow AMA guidelines at AMA fields, and don't do stupid stuff that's is going to bring negative media attention to multirotors.
You see helis have had the abiltiy to do all sorts dumb stuff for years. It hasn't been until recently that companies have made flying a multirotor heli a skilless event that's cheap enough for just about any idiot with $50 bucks to get his feet wet.
Now these machines are in the hands of many who are absolutely clueless. They know nothing of safety or the danger these little machines pose go others. Hell a bird can bring down a jet, now lets fly a Lipo battery and a gopro into the clouds so we can post the video on YouTube.
As a pilot I know exactly where this is going. All of the multirotors (except the toy grade) are going to be taken away from the general public. Any of them that have the abilty to be used in a commercial capacity will be controlled in such a way to hold the operator responsible.
An example would be deeming them as experiential aircraft and subject them to FAA regs. This will drive the price up so high that the masses of uneducated morons that fly phantoms in the clouds for YouTube will be out of the game.
It will take time, but commercial use of multirotors is comming. Transponders, and FAA certifed GPS will be in these machines and they will be in use. Somthing that cost 10 grand now will be 100 grand but this tech is here to stay. It just won't be in the hands of a regular guy. Mark my words, toy multirotors are the olny thing people " in the Hobby" will have to play with.
There is so much risk allowing things to continue as they are. These are dangerous enough as they are, imagine if terrorist used these against the US in the same way we have used them against others. The US just won't allow that to happen. I give it five years or less until you see major changes with respect to multirotor/drones/uav/fpv piloted vechicles operating in the USA.