Quite frankly with the advent of bitcoins new cryptocurrencies are being introduced day by day. that could be a potential reason of decrease in value of bitcoins because the crowd that bitcoins would have generated in terms of demand is now divided into small segments.
Is there a way to introduce them without hampering the present demand and supply of bitcoins and at the same time assuring that they can move up nicely in the market.
Most people were disagreed about your statement, new altcoins means nothing to affect bitcoin price, maybe some altcoins could attracted people to switch their investment, out of bitcoin for some time, but bitcoin price will recover again.
But most altcoins can not affect bitcoin price at all. On the other hand, uncertain news about bitcoin or exchanges will be banned has been proven could affected global market price, due to panic sell or people choose to sell-off instead of holding.