> 7447B/C rated frequency rises upto 1700 MHz

Already 7447A had 1.7 GHz maximum rated frequency, as discussed a year ago :-)

> frequency of 7457 stayed on 1267 MHz all the time.

Interestingly, there was a 1333 MHz 7457 listed in 2006 as "No Longer Manufactured" (MC7457RX1333PC*, RoHS-compliant replacement part was 1267 MHz), while 7447 was kept at 1267 MHz.
With the advent of the higher-clocking 7447A, Motorola/Freescale simply EOL'ed the 745x line. I don't remember I ever read an official explanation as to why no 7457A/B/C or 7458 was released.


* I also found mention of MC7457RX1333PB, but not sure if genuine or fake part number