Reading the history, Motorola abandoned the 68k (Apple started switching to PPC that same year).
I don't know for sure why Moto dropped it, but lifting from Wikipedia:
While the Motorola 68040 offered the same features as the Intel 80486 and could on a clock-for-clock basis significantly outperform the Intel chip, the 486 had the ability to be clocked significantly faster without suffering from overheating problems, especially the clock-doubled i486DX2 which ran the CPU logic at twice the external bus speed, giving such equipped IBM compatible systems a significant performance lead over their Macintosh equivalents
I don't know for sure why Moto dropped it, but lifting from Wikipedia:
While the Motorola 68040 offered the same features as the Intel 80486 and could on a clock-for-clock basis significantly outperform the Intel chip, the 486 had the ability to be clocked significantly faster without suffering from overheating problems, especially the clock-doubled i486DX2 which ran the CPU logic at twice the external bus speed, giving such equipped IBM compatible systems a significant performance lead over their Macintosh equivalents