I believe there is a tiny market out there of wireless HDMI. I say tiny because the cheapest receivers are above $1000. If one could send an HDMI signal reliably over WI FI, I wonder why it hasn't been done yet...
There is of course HDMI over ethernet, so again I don't see why a solid WI FI connection couldn't do it.
Ok now to my actual intended post...
I don't think that they would come out with a wireless connector for the Tablet. What Apple will want to do is integrate the Tablet as much as possible with the Apple TV. Since Apple is mostly about convergence, I don't see them coming out with an accessory for the Apple TV.