Sandybridge is a micro-architecture and Core i7 is a brand. If Intel is happy with the current naming scheme they are not required to change it. The "Core" branding that started with Merom in 2006, changed to Core 2 and then Core i7. The i7 branding isn't even two years old. Certainly Sandybridge will replace the Nehalem architecture, but it doesn't require Intel replace the i7 branding. The certainly can if the need to, but it doesn't mean they will.
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