Bitcoin will never reach the mainstream because there are far too many crooks, scammers, hackers and the like preying on everyone else aswell as each other. And because of the anonymity they are much less likely to be traced.
Unless the whole business has more accountability it will always remain underground and be treated with suspicion by mainstream consumers and businesses alike.
With difficulty reaching such high levels in a few months putting mining outside the realm of 99% of current miners I forsee the interest in BTC dieing out quite rapidly and the whole charade collapsing.
Dramatic, yes. Probable, yes.
I think that it has less to do with the scammers and more with the fact that there aren't very many legitimate uses right now. There's nothing worth spending bitcoins on, unless you're buying drugs. Most people won't bother with bitcoins because they have no reason to.
However, even if every single Internet user starts using bitcoins, there simply aren't enough Internet users for it to become mainstream. Less than a third of the world has Internet, so large businesses would lose money if they were to switch solely to bitcoins. Bitcoins also fluctuate much more rapidly. Businesses would have to change prices day to day, whereas with traditional currency they don't have to. It would be too much of a risk and not enough of a gain to make the switch. Why bother accepting bitcoins when people have no choice but to pay with fiat anyways?