> 10500 BC was the last time, when is the next?
The correlation is not exact at all. When Bauval and Gilbert published their book, they portrayed the alignment with the stars of Orion's Belt as large blobs against the three large square bases of the pyramids. They had to do this to make it seem like the pyramids matched the stars exactly, but the association is only vague.
To support his theory, Bauval has invoked Badawy and Trimble's theory of the stellar alignment of the KCS and KCN shafts. They said the KCS shaft lines up roughly with Orion's Belt, but Bauval, inspired by the brilliance of his own OCT, has suggested that the KCS shaft aligns specifically with Al Nitak (the lower culminating star), since this is the star that corresponds to Khufu's Pyramid in the Giza alignment.
Bauval has gone further. He has said that the KCS-Al Nitak alignment can be used to date this pyramid, to 2450 BCE. This flies in the face of orthodox chronology, and of course the conspiracy theorists love this.
Bauval has also suggested a stellar alignment for the two lower (QC) shafts, and orthodoxy for the most part accepts the combined Badawy-Trimble-Bauval stellar alignment theory of the shafts in a general sense, while rejecting Bauval's matching the KCS shaft specifically with Al Nitak. Indeed, Krupp for example says that the KCS shaft points at the middle star Al Nilam almost precisely for the year 2550 BCE, an accepted date for the building of this pyramid.
In more recent times, Magli has stepped into the debate, and pointed out that the final portion of the KCN shaft, set at a slightly lower angle than the overall slope of the shaft of 7:11 (according to Gantenbrink) also points to Thuban rather precisely in 2550 BCE, thus "locking in" KCS's orientation to Al Nilam. This orientation conflicts with Bauval's hypothesis of KCS's orientation to Al Nitak, and this further undermines the OCT.