It depends how badly you need it atm. I've also been considering not waiting and just buying a refurb and saving some money, but I'd hate to be disappointed if in a month, some great changes came. My current PC is still holding together (barely...) and I bought a refurb iPad 2 to hold me over, so I'm hanging on for now...
I don't think anybody can give a definitive answer, but I think there's a good enough chance that the MBAs could come that you should wait if you can. If you have other devices that can act as a substitute for a few more months, be patient. I think once WWDC rolls around (less than two weeks) there is a chance we'll hear more. Wait til then at the very least. If you can't, the $200 savings on a refurb should make you happy enough!