The entire "limit" issue is perhaps best addressed
here. There's really no need for clones.
, no. Bitcoin can function alone now, but multiple independent systems in the same class are capable of amplifying the overall effect.
There may also be growing realization that trading BTC/LTC or BTC/XRP is preferable to BTC/USD or any other fiat denomination. There is arguably greater risk in having exposure of any kind to the traditional financial system, and remaining in the crypto environment is much faster for many activities.
Individuals who feel comfortable with relatively concentrated transaction processing power should have no problem with Bitcoin. Those who do not may prefer Litecoin, Ripple, or any other variant that might gain traction.
SatoshiDice would cripple and probably destroy any chain incapable of sustaining itself, while acting as a rite-of-passage for those that can pass muster; the stronger a source of revenue, the better.