There is no end in sight yet as to price increases on fabric. Nor will there be, at least until the 2011 crop is harvested so we know how much cotton (supply) is available.
The longer the manufacturer - or retail store - or customer - waits, before placing their order, the higher the price will be. There is only so much 2010 fabric left to be sold at the wholesale level, and after that supply is exhausted all shops will have to buy new goods at the current higher prices.
That said... I don't see prices doubling. My best (semi-educated) guess is that unless something new and awful happens, wholesale prices are likely to go up another 50 cent - $1 by the end of the year. Which would translate into (USA) retail prices for new prints being about $13 / yard in those stores which charge full-price.
It's not the end of the world, and we will still sew, but we will make our choices more carefully and probably will not do so much buying "on a whim".
If you do not have sufficient backing or batting to finish all the projects that you HONESTLY think you will complete in the next year-and-a-half or so, then it probably would be wise to stock up on those items if you have the funds (and storage space) to do so.
If cotton prices do come down again, it will take a while before that will be reflected in the retail price of fabrics. And the prices will probably never come all the way back down again. (Gasoline never did...)