The MacBook Air will become the tablet - which has been the plan all along.
The Air was never really intended to gain mainstream traction (simply look at the entry-level price tag). It was merely a way for Apple to learn valuable lessons about manufacturing such a thin device. Lessons about battery, SSD, physical space challenges, etc. Those lessons combined with what they learned with the iPhone will culminate in the revamped MacBook Air.
Besides, with a tablet in the mix, I no longer see the point of an Air.
And with the myTouch on the market, yet another reason it will not be called macBook Touch, but pick up the Air moniker.
MacBook (entry level laptop)
MacBook Air (tablet)
MacBook Pro (pro level laptop)