Probably not much other than not being able to resume from suspend and/or hibernate by hitting a key on the keyboard.
A bit of extra background for why it's just 'probably':
HID is a communications protocol primarily designed for input devices (keyboards, mice, game controllers, etc) intended to be independent of the underlying connection (HID is used over at least USB, Bluetooth, ZigBee, and I2C, and possibly other hardware interconnects). Most modern USB and Bluetooth input devices are HID devices, though some laptops continue to use PS/2 internally instead of USB+HID for their keyboard and touchpad for power efficiency reasons.
The thing is, the HID protocol isn't just used for actual input devices. The protocol itself is rather lax, and quite a few things present as HID devices that either don't fit what many people think of as input devices (for example, audio controllers or USB-connected phone handsets (for use with VoIP systems)), or that quite simply aren't input devices (a lot of USB connected uninterruptible power supplies and software protection dongles are also HID devices). Some of these devices present generically as a keyboard or mouse instead of something more specific.
As a result of this, it's possible that the physical device listed as 'HID Keyboard' may not actually be a keyboard, and may serve some other function in your system, in which case disabling wakeups from that device may either do nothing at all, or might actually cause something to stop working (though this is very unlikely). However, unless you see more than one keyboard listed this is exceedingly unlikely.