This blown up rumor is an old one but has turned out to a report now, yes the Japanese blog reports that the next generation will be much thicker not slim as the advanced technology should do but it will have retina display for sure. The screen sizes will be for sure the same one i.e 9.7 inches. The main focus by the Macotakara was on the smart cover of the iPad 2 which wont fit on the next generation iPad.
According to Asian supplier which provides part for next iPad, next iPad has same size of screen, but case may be thicker by unknown reason. Current iPad cases, which covers backside, will not be compatible with thicker next iPad.
This cover/case is actually of the original iPad 3G according to 9to5Mac, so nothing’s yet confirmed. Till now we just know rather a rumor that the next generation iPad will launch in the early 2012 as the other iPad’s also launched in the Q1 of each year.