We heard gossip that HD 4870 X2 (R700) might be released with 2GB of memory. Still, a trustworthy source confirmed that samples with 2GB of memory will reach manufacturers in mid-July.
Referring to graphics card manufacturers, the source claims that the "senior brother" of ATI Radeon HD 4850/4870 will be officially introduced late in July, when AMD starts shipping reference cards with 2GB GDDR5.
In mid-August, partners of AMD that plan on releasing custom products will start receiving 4870 X2 (RV770XT) GPUs.
As you know, Radeon HD 4870 features 8 x 512 Mbit GDDR5 chips produced by Qimonda. We've seen 16 chips on images of R700 - 8 per side. Thus, 2GB capacity can be reached only by using 1Gbit chips. According to the source, Qimonda launches shipments of such chips this month. Besides, Hynix also has similar offerings.