My advice would be to buy a MBA in the meantime, while waiting for the rMB to become the superlative computer the MBA had long held the promise of becoming.
I was bowled over by the MBA when it appeared in 2008, and resolved to get one at some stage. Initially, - while it looked gorgeous - the form factor was stunning - was the first computer Apple made that used SSD for memory, and was exceptionally portable - it was massively underpowered, and the specifications were limited.
My first MBA was the so-called "Rev C" which I bought in 2010 - and it was a terrific computer. But the MBAs I bought in 2013, and 2014, (a 13" and an 11") blew it away - they are astonishingly good machines, and my only quibble - and it is a minor one, as the rest of what the computer has to offer is so good - is that the screen is not as good as that of the rMB.
But, I'll not buy a rMB until it is a bit better - and more powerful - than the machine currently on offer.