Yes, it can be overclocked. Here are the details:
The Pi bootloader still follows the overclocking parameters that's usually placed in the
/boot/config.txt file despite
raspi-config not having any overclocking settings for the Pi 3.
raspi-config doesn't have any of the overclock good stuff since the Pi 3 doesn't officially support overclocking.
Basically, what you'll do is manually edit those parameters in said file. I'll assume you're already familiar with the Pi so I'll leave out the how-to-edit part.
My stable frequencies were at 1.4 GHz for ARM,
sdram_freq were at 500 MHz. 7 overvolt.
tail -n 4 /boot/config.txt
Note: I'm not responsible for any damage you may do to your Pi. Tests were done with adequate cooling measures (heatsink, fan, air-conditioned room). PandaLion98 and related entities are not responsible for any damage that you may do to your Pi. Do at your own risk.