Obviously a lot of people look real stupid right now. Which is why making predictions is a tricky business. And in hindsight, if you voted no back in 2009 you probably should've noticed that he was getting better on HCs and still very young. Back to back SFs at USO and a win in Australia so voting no was probably stupid regardless, but I will say this, the surface at the USO has changed pretty dramatically to Nadal's benefit since 2009.
I could be wrong here, but I don't think I ever believed that Nadal would go slam less at the USO ala Borg for example, but I also don't think he'd have 4 USO titles now if the surface wasn't playing into his hands in recent years.
This thread is like making a "Will Nadal ever win the AO?" thread after 2008. Many people then would've had good reason to say no as well, and they would still be wrong, but at the same time he has only 1 AO title and that's due to a combination of tough luck and tough opponents when he could/should have more. The same thing (or the reverse i.e 4 AO titles and 1 USO) could've happened at the USO.
Back in the mid-late 00's I'd say Cincy (where Nadal has just one title) and the USO were a lot alike, but now they aren't, just as an example, and that's helped Nadal. Borg is a good analogy as well because he was clearly good enough to win the USO even though he never did, primary cause being very tough competition, closely related to Nadal at the AO. You give Borg the surfaces that Nadal gets to play on and I bet you he beats Connors and/or McEnroe at least 2-3 times.
So while I do think it's pretty stupid to say definitively that a guy who just won the AO in 2009 at 22 couldn't ever win the USO, I'd also say that if you gave a decent reasoning as to why you thought he wouldn't do it back then I would've given a pass on it. I can't say honestly that I would've voted correctly on this poll back in 2009. I could've easily been lumped in with everybody who's getting roasted now. I'd also point out that the user namelessone on the first page is/was a big Nadal fan and he was skeptical too, so it wasn't just non Nadal fans (though clearly some just voted with their hearts and not heads) that were piling on him.
It was a different time even as recently as 10-11 years ago. I can bet you that 99% of the posters here, even the ones that are jumping on this old thread now, would've never expected all of the Big 3 to still be playing today and still be the best players on the planet either. All of them could play into their 40's as well. We know that now, but even just 10 years ago the career expectancy of a pro tennis player was to be retired shortly after 30, like Sampras, and if you got to 35 you were lucky or needed a mid career break like Agassi. Different times, different perceptions.