earning from trading is possible but would take alot of time and skills/luck, but most likley btc will be a side income for most of us.
There are actually a lot of people now that has bitcoins as their main source of income like going full time bitcoiner. It doesn't necessarily mean that they have to change what they are doing, they only needed to be changed in the way they are paid.
In my opinion, Bitcoin is just like a beta before the real currency comes up.
I don't know, it's just my opinion. That new currency will probably be the worldwide one, used by everyone. For now, for some (most) of us it's pretty hard to use BTC.. I have to drive +500km to get to a BTC ATM. So I wouldn't like to get my revenue in BTC. I prefer having it as a saving currency.