It's not going to happen because 'coins are hard to carry'? Uhm... At least Canada, the whole of the European Union, and I'm pretty sure Mexico all have $1/$2 coins, and somehow -perhaps we Canadians are just made of hardier stuff- we have survived.
I'm sure there are many arguments to be had over this, I don't know them, but I think 'coins are hard to carry' is basically a non-argument in light of the fact that many nations already do this and it hasn't caused them to grind to some kind of catastrophic halt.