Lux Research released a new report (Is Graphene the Next Silicon ... Or Just the Next Carbon Nanotube?) on the graphene market, in which they forecast that the graphene market will grow to $126 million in 2020 (up from $9 million in 2012). It's an impressive growth - but the overall market will remain small. Most of the growth will come from graphene nanoplatelets (NGP) for the composites and energy storage applications. Graphene sheets will remain mostly in the lab.
According to Lux, the leading companies will be XG Sciences and Vorbeck Materials. Vorbeck is selling higher margin conductive inks, while XG supplies GNPs to corporate channel partners. Regarding newer startups (such as Graphene Technologies, Grafoid, National Nanomaterials, Xolve and Haydale), Lux says it is simply too early to tell.
Back in October 2012 IDTechEx released their own graphene market report, coming to basically the same conclusion (they forecast that the market for graphene will only amount to $100 million in 2018).