You say that as if a 20-year-old 7-foot center who got rookie minutes in his first year in the NBA is a done-deal bust before his second year starts.
I think Spencer has looked quite good this preseason with the exception of his two outings against Oden. Considering that Oden is not only a physical beast but also the most anticipated young player since LeBron, Hawes' struggles against him don't overly worry me. He's got time, both to learn to play against more physical players, and to fill his body out. Looking at the '07 draft, there are a grand total of three players I'd trade Hawes for straight up right now, and they were drafted 1-2-3. That's not to say that some of those guys won't end up better (Fernandez, Thornton, and Thaddeus Young would lead my current list of potential all-stars in the don't-trade-Hawes-for category, with Sessions a rising dark horse) but Spencer has the potential to be an all-star center with great offense and average defense. Even if he'll never be a defensive brute his numbers have improved in the preseason relative to last year (per48: rebounds 13 vs 12, blocks 2.5 vs. 2.1) and he's 20. You don't write that off after a couple of bad games against Oden.
You say you're not ready to say "I told you so", but I don't understand how that could even be under consideration at this point.