I'd normally agree, but the Executive Producers of Smallville have been playing fast and loose with the comics continuity for a while now. Morgan Edge and Perry White meeting Clark before he left Smallville, for example. And I can't imagine how Clark can become Superman without Lex tying two and two together about Supes' secret identity. And frankly, I think that Smallville's Lana only common trait with comic's Lana is her name.

With all the angst that a Lex/Lana relationship could bring to the series (also known as ratings) I think it could happen - for a while.