That is understandable, because few if any (LTC, DOGE, ?) altcoins have any economy supporting them. If they don't gain in value, they lose it, and quickly. With Bitcoin, the economy is constantly growing and the lead time with real-world projects is so long (6-24 months) that it is virtually shielded from short-term price fluctuations. Eg. the Malla project is fully funded for 2014, and only if Bitcoin loses nearly all of its value, would its growth (in a sense of increasing contribution to "real" economy with bitcoins) be hampered, and even that only from 2015 on.

Only if existing bitcoin economy participants start closing shop in droves, mitigating the effect of the myriad of new projects, would there be any chance for Bitcoin to even stall in the long term. Anything else is supportive to continuing price appreciation.

(Yes I acknowledge that the closing of exchanges counts in the equation.)