Do you think that will appear new altcoins can challenge Bitcoin ?
Definitely, with time the altcoins will surpass Bitcoin. Bitcoin has the advantage of being the first on the market, but its targeted application to products and services is limited. It's hard to see the crypto-economy reversing itself, while the fall of one currency is not only believable, but as with all things - inevitable. It may take a long time, however, so an investment in Bitcoin is still a very plausible strategy!