Motorola 7457 Upgrades posts rumors from a source "in the know" on Apple's 2003 chip plans:

    According to the source, the next revision of the Motorola G4+ PowerPC, the 7457, will top out at 1.33 or 1.4GHz (1.0GHz, 1.17GHz, 1.33GHz, 1.40GHz?) in February 2003, and will stick there until July 2003, when another 7457 revision should arrive, promising to push the chip up to a more respectable 1.83GHz (1.50GHz, 1.67GHz, 1.83GHz).

This information echoes some of the information from this anonymous source -- which also pegs the 970's successor to be due in Q3 2004.

The only contradictory information we have is that Dual 1.5GHz PowerMacs have existed within Apple for some time now... but this does not give any indication to Motorola's ability to produce these in volume.