The Galaxy J2 has barely been on the market for a month, and Samsung seems to be already working on a Galaxy J3. The Galaxy J3, with model number SM-J3109, has been spotted on the GFXBench benchmark with pretty much all of its specs listed; GFXBench doesn't seem to have the device in its database anymore, but we can see an SM-J3109 over on Geekbench.
The J3's specs include a 5-inch HD (1280×720) display, a 64-bit Snapdragon 410 processor, 1GB of RAM, 8GB of internal storage, an 8-megapixel rear camera, a 5-megapixel front camera, and Android 5.1.1. These specs look to be slight upgrades over what the Galaxy J2 offers, such as an HD screen instead of a qHD one and a more powerful processor. The model number is an oddity – based on other Galaxy J devices the model number should be SM-J300 instead of SM-J310 (the fourth digit isn't as surprising as Chinese variants of Samsung devices usually have four digit model numbers), though this could be because the J3 is far from an official launch.
We are currently working on a review of the Galaxy J2, and we can only hope Samsung doesn't launch the J3 before we're done.