As the Haswell CPU is meant to be aimed more at the mobile tech side of things with increases power efficiency and a boost to clock speeds. Is it worth waiting another month or two for the release of notebooks with the Haswell CPU???
Current guess-timates indicates that the Intel HD 4600 (GT2) is estimated to be about 20% more powerful than a similarly clocked Intel HD 4000. Note that while all mobile Ivy Bridge CPUs have the Intel HD 4000 graphic core, they do not all run at the same clockspeed. Ivy Bridge CPUs with the "Y" desgination have the lowest performance to decrease power consumption. "U" model ivy Bridge CPUs are used in ultrabooks and are the 2nd slowest Intel HD 4000 clockspeeds. Dual core i3/i5/i7 "M" CPUs will more or less have "standard" performance. The quad core i7 "QM" CPUs will have Intel HD 4000 with the highest clockspeed.
All together, there are about 7 or 8 different clockspeed variations of the Intel HD 4000 in mobile Ivy Bridge CPUs. The Intel's GT2 graphic core will exist for both desktop and mobile CPUs. On the desktop side all Intel HD 4000 run at the same speed and it is expected that GT2 (Intel HD 4600) will be the same as well.
The Intel HD 5000 (GT3) series will be exclusive to "higher end" mobile CPUs. There are rumored to be 3 different models representing different clockspeeds HD 5000, HD 5100 and HD 5200. The hardware difference between GT2 and GT3 is primarily 20 shaders vs 40 shaders. As a comparison the Intel HD 3000 has 12 shaders and Intel HD 4000 has 16 shaders.
By "higher end" Haswell CPUs, I would guess only the Core i5 and i7 CPUs will have the GT3 version of Intel's iGPU. Additionally, I am guessing that "U" model Haswell CPUs for ultrabooks will only get the Intel HD 4600 (GT2) simply due to power consumption concerns. The Intel HD 5100 and HD 5200 may only be available on the quad core i7 "QM" CPUs. The rumored estimate of the performance of the GT3 version is estimated to be anywhere from a 50% to 100% increase over the Intel HD 4000. That could mean that the Intel HD 5200 might be as powerful as the Radeon HD 7660g in the A10-4600k.
This is all pure speculation.
CPU clockspeed is not expected to increase by much since the primary goal of Haswell is to reduce power consumption.