Nintendo will be updating the 3DS next month which will see a few new features added to the handheld.
One thing that many users have been clamouring for is the combination of eShop balances between the 3DS and Wii U. Right now when you add funds to your 3DS those funds are only available on the handheld. In the same respect funds added to your Wii U for eShop purchases and downloads are only usable on your Wii U. Once the update comes you will be able to use the same Nintendo Network ID for both systems which will allow the funds to be pooled between the two systems.
Users who have a Wii U already have the NNID. Connecting it to your 3DS will let those funds be used on your 3DS as well.
Another new feature being added to the 3DS is Miiverse, the community that is currently only available on the Wii U. With the previous announcment that Nintendo is going to be allowing remote Miiverse access from smartphones and computers this now allows those with only a 3DS to join in on the fun.
The handheld will ALSO be finally getting a YouTube application which will allow viewing of those videos on the 3DS. With the two screens you can watch a video on the top screen while still browsing for content on the bottom screen. There was no firm date for the application to be released, though it was stated the the Wii U YouTube application will be updated on December 2nd.