C2D is in fact in the mainstream market in the past 2-3 years and if i5 is the one in the mainstream now, why is i5 not replacing it? why would users opt for a processor with higher power consumption than new one with lower where both offers the same or better performance for the latter?

AFAIK, we can look back in the history as how Core Duo was replaced by Core 2 Duo, as we don't see much or none of CD anymore after the introduction of C2D.

assuming i5 is not replacing C2D:
1. why would all manufacturers are refreshing their lineups with i5, which used to be on C2D? isn't this a sign of phasing out instead of opening up a new market?
2. why benchmarks are comparing head-to-head performance between C2D and i5? (same for i7 vs C2Q).

or like what Eugene91 has pointed out, why both C2D and C2Q are listed under previous generation products? if the new Arrandale platform is not meant replace C2D and merely to serve a different segment of the market, C2D would have remained on the main page, just like Pentium, Celeron and Atom.

the thing is, products can be replaced, so is the market.

not looking for an argument here but solely to seek solid explanation and proof on your claims. anyway, i would expect someone from Intel to know its company's products better.