I didn't ignore the ticket sales, and I already said it's possible that an album at the time of This Is It might have done OK. But the ticket sales don't necessarily translate to album sales. After 1993, his albums sold much fewer than before; just as History sold much less than Dangerous, and Invincible much less than History, any future album would have sold even less. Album sales were declining for the music industry in general, so obviously they would decline for someone already past his prime like MJ.
Again, I don't rule out an album doing OK in 2009, but it wouldn't be the grand comeback that some fans think it would have been. I don't think him releasing an album that would only sell 3m at most was necessary; it would have been dismissed as a failure by MJ's standards, just as Invincible was.
The reason why History sold less than Dangerous was because it was a double disc album, which meant that it was more expensive than a standard single disc album. Also, the allegations didn't help. Michael also stop touring the US after the Bad Tour, which no doubt affected the sales in his homeland.
Regardless, History was a big success in Europe and its single Earth Song is Michael's second most successful single after Billie Jean in the UK. All the singles from Michael's History album cracked the top 10 in the UK, which wasn't the case for the singles of his previous albums. Aforementioned Earth Song also became Michael's first ever song to hit #1 in Germany, with They Don't Care About Us becoming Michael's second #1 there. As Michael was losing popularity in the USA, he was gaining it in other music markets.
The reason for Invincible not doing as well as his previous albums was down to lack of promotion and Michael himself abandoning the Invincible project. Remember that Michael performed at the American Bandstand and Clinton's gala in April 2002, which was just a few months after the release of Invincible. If Michael wanted to, he could have performed songs from Invincible during those performances which would have definitely helped increased the sales of Invincible.
Regardless, Invincible sold 7+ million copies, which was a success for an artist in his 40s and with all the scandals. I believe that had Michael released an album in 2009-10, it would have matched the sales of Invincible. With all the promotion and hype of Michael comeback, his new album would have done well. Would it have done as well as Thriller, Bad, Off The Wall, Dangerous, History? No, but it still would have been commercially successful. I think Michael was realistic in the sense that he knew that he was past his commercial peak. Michael's contemporaries such as Madonna was still commercially successful in 2008 with her Hard Candy album. There is no reason why Michael couldn't have been as well during that time, as he was a bigger star.
Yes, MJ still had plenty of fans worldwide, but I'm mainly speaking of America. His last top ten hit on the Hot 100 was in 2001. "One More Chance" in 2003 flopped. And you can't ignore the fact that after the second child molestation scandal, MJ was a huge laughing stock in America. He was the go-to punchline in pop culture; tons of shows, movies, comedians and people online would make fun of him nonstop.
America isn't the only country. As I mentioned above, Michael stopped touring USA after the Bad Tour. He wasn't too bothered about the US market anymore. He was trying to focus on the European, Asian & South American markets in the 1990s.
One More Chance came around the same time the second allegations broke out. It was never going to be commercially successful. It still managed to reach top 10 in some European countries, so it wasn't a total flop.
Michael not having any top 10 hits in USA after 2001 was down to the fact that singles such as Cry weren't released in the US. Butterflies despite its popularity was only released to radio airplay. It peaked at #14. Had it been released as a proper single, it was have no doubt cracked the top 10.
So after You Rock My World, the only other song that was released as a single in the USA during Michael's lifetime was the aforementioned One More Chance, which was unfortunately doomed from the start, because of it releasing at the worst possible time.
P.s. Michael has had two posthumous top 10 hits in the USA with Love Never Felt So Good and Don't Matter To Me, so it isn't all too bad.