The cryptocurrency space is innovating at a breakneck pace, trying to chase the always-increasing requirements of users. The invention of new technologies makes older designs obsolete, and this may very well be what’s happening with Bitcoin right now. As it is really hard to make any substantial changes to its code now, second- or third-movers gain a significant advantage by virtue of being able to implement breakthrough developments that are inapplicable to Bitcoin right now, but should have, in hindsight, been a part of it since the start.
One of the principal points of Bitcoin was to provide its adopters with the ability to conduct any transactions they want, without fear of having their identity exposed. The emergence of those who accomplish that more effectively may one day challenge bitcoin for the top of the cryptocurrency heap.
While the Bitcoin Foundation and its Core Development Team continue to add what they feel are the most significant and easily implemented changes; other technologies, such as CryptoNote can provide a possible look into the next generation of cryptocurrencies themselves, it enables the coins that use it a few significant features that Bitcoin and the more traditional altcoins cannot perform at a fundamental level. We can't say if Bitcoin will be challenged by CryptoNote or not, but it has all the tools necessary to give it a real run.
Bitcoin is ironically, both anonymous and traceable. As you likely know, every transaction can be tracked on the blockchain and be linked to the public keys involved in the transaction. In this way, researchers, law enforcement or anyone else determined enough can follow coins through the system and link them to the wallets that held them. Wallets themselves are anonymous in theory and there are plenty of places where a wallet can be created without any link to the physical world, but if any wallet gets linked back to a user (through an email or bank account for an example) ...