NL600...should my opponent fold KK preflop?

[HoldEmKillah]

Results of this hand don't matter although I will post them at a later date anyway. The point of this post is that it got me to thinking about my opponents' hand and weather or not it would be correct for him to fold KK preflop. The Button in this hand is dealt KK. I have ??. I'm sure that my opponent must have some sort of read on me alhtough I'm not sure how deep of a read it is. But I'm not a LAP and have not been playing reckless whatsoever. Do you think he should lay down his KK here?

Party Poker No-Limit Hold'em, $ BB (6 max, 6 handed) converter

CO ($672.65)
Button ($616.35)
Hero ($887.65)
BB ($361.85)
UTG ($780.65)
MP ($1065.4)

Preflop: Hero is SB with ??:. Hero posts a blind of $3.
<font color="#CC3333">UTG raises to $20</font>, <font color="#666666">2 folds</font>, Button calls $20, <font color="#CC3333">Hero (poster) raises to $52</font>, <font color="#666666">1 fold</font>, UTG calls $35, <font color="#CC3333">Button raises to $200</font>, <font color="#CC3333">Hero raises to $422</font>, UTG folds,