There is a more interesting implication in that section actually.

Light glinted from the reflection of Albus's half-moon glasses as the old wizard slowly shook his head. "I think that would be unwise," Albus said. "For reasons beyond the obvious. It is dangerous, that place which Merlin made; more dangerous to some people than others."

'To some people than others' implies Harry. Ergo, it would be more dangerous for Harry to go there.

Ergo, there are other things in the Hall of Prophecy which would effect Harry.

Ergo, there are more Prophecies about Harry there. We already know or can suspect one, the HE IS COMING one. (Which incidentally I suspect is 'TEAR APART THE VERY FABRIC OF SPACE AND TIME' and that [rot13] Gur Zna Haqre gur Ung, naq gur bevtvangbe bs n ohapu bs gurfr cynaf vf n Shgher Uneel jub unf tbggra nebhaq Gvzr Gheare erfgevpgvbaf. Ur shpxrq fbzrguvat hc naq vf gelvat gb svk vg, be ur qvqa'g naq ernyvmrq gung ur arrqrq gb qb gurfr guvatf gb rafher uvf bja gvzryvar.)

Also from this, since Dumbledore will not take him there, we can assume that whatever it is that Harry might discover there would be detrimental to Dumbledore.

On a meta note, it is also a reason (beyond the many others) for which Eleizer would have had to deny Harry a phoenix. Far too much freedom of movement for the plot to remain on any semblance of rails.