Speed increase does not only rely on an increase in the core clock speed, remember that. You can increase performance/speed in a number of ways, and the most common two is to push the clock speed (up the GHz) and to enable Hyper Threading on the CPU (one core is seen and used as two, making applications requiring more threads run much faster). Other methods include a refined architecture ("Sandy Bridge" design over something like "Nehalem" design), smaller manufacturing process (32nm improvement over 45nm), increased FSB speed (newer 1333MHz FSB over older 800MHz FSB from CPU's like Pentium 4) and physically increasing the core count on the CPU (Quad Core and Dual Core over single core CPU's).
Expect to see more of the refinements rather than an overall increased clock speed. A good comparison between Sandy Bridge and Ivy Bridge would be almost the same as comparing the Intel Core i7-975 to the Core i7-980X. Differences aren't in clock speed (both are 3.33GHz reference), but rather in design:
- 975 has 45nm manufacturing process, 980X has 32nm
- 975 has 8MB Cache, 980X has 12MB
- 975 has 4 cores, 980X has 6 cores
- Both CPU's have Hyper Threading Technology
- They have the same bus speed
But still the 980X is a much more powerful processor, only due to the design refinement.