In short, yes - for some keyboards. The technique used to intercept and sniff on some (mostly older than 5 years) wireless keyboards can be pretty easily leveraged to allow an attacker to transmit back to the receiver on those keyboards.

You say you are aware of [blog posts that discuss how to intercept wireless keyboard keystrokes](http://samy.pl/keysweeper/). If you are, then you know that those methods include breaking the 'encryption' of those devices. The 'encryption' used by those keyboards is as simple as XOR'ing the data with the MAC of the keyboard. Now consider an attacker has successfully obtained the key of the encryption, from there, he/she can use the same radio transmitter they used to sniff to start transmitting, instead of just passively intercepting.

Since this is [RF](https://www.google.co.il/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwim4pK_6IrTAhXBjiwKHbkaBtUQFggjMAE&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FRadio_frequency&usg=AFQjCNEMvu5zytNjvWgORkUEHv5xOn6X-A&sig2=_HHdqWlGBIqLb__u_fVWiQ) we're talking about, there is no state-full 'connection' between the keyboard and receiver other than the predetermined protocol. This enables the attacker (that now knows the protocol, since he/she successfully sniffed the traffic) to start transmitting to the receiver pretending to be the keyboard.

An HID attack can then take place. The attacker could do many malicious things to the victim machine. Although, if the owner is using the machine, the attack is easily thwarted, simply by injecting random keystrokes or by disconnecting the receiver, so the attacker must initiate the attack at an opportune moment.

**Edit:** According to [daniel](https://security.stackexchange.com/users/8072/daniel)'s comment, I have tried to make my answer clearer and more accurate.