I've tried to find some info about this but failed.
I'm considering swapping BS for Engi in Cata, but I'd like to know if there will be new versions of Hyperspeed Accelerators and Nitro Boosts, as those are the main reasons for the switch.
The old Accelerators are naturally very tempting now, but if there's no new and improved version, then other enchants are probably better at lvl 85. Of course, there's also the possiblity that some ilvl limit would be added to these old enchants, preventing you from putting them on new Cata items.
So, any word yet?