This remains unconfirmed at this point in time. Rumor is floating around the web that the latest firmware update for the Nintendo 3DS held within Super Mario 3D Land has unlocked some extra CPU power for developers to use in their future games. According to the rumor, the update unlocks part of the second CPU inside the 3DS for use in game development. The second CPU was apparently dedicated to wireless functions prior to this and could not be accessed for use in games. But as of now, the update is rumored to unlock around 25% of the second CPU's power to games. This may end up becoming an option that you can select in games, similar to the ability to overclock the PSP's processor. However, the rumor also states that enabling this may also disable or negatively impact some wireless functions that rely on the second CPU. As of now, this does remain a rumor, so take with a grain of salt until further confirmation. If it ends up being true, it will be interesting to see if and how this may impact future 3DS game performance.
Another part of this rumor also states that developers may be able to patch 3DS games via the eshop, in the event of bug fixes or perhaps downloadable content. The article that this information came from also states that the current limitation for 3DS eshop games is 512MB.
