At this point it may make sense to wait, however, you will have to wait a few weeks for the computer to actually ship. If battery life is what you are after, the current notebooks currently get excellent battery life. I cannot speak for the 13 inch, but my 15'' rMBP gets about 7-8 hours of life under lite/normal usage with the screen at about 1/2 brightness. I bought mine brand new, but the referbs are always a great deal. We currently have a 17 inch 2010 model that was a referb and have had 0 issues with it. You get the same great 1 year warranty that covers just about everything too.
If you need it, buy it now, any upgrades are not likely to be significant enough for the average consumer to notice a difference.