"Gates himself has strenuously denied making the comment. In a newspaper column that he wrote in the mid-1990s, Gates
responded to a student's question about the quote: "I've said some stupid things and some wrong things, but not that. No one involved in computers would ever say that a certain amount of memory is enough for all time." Later in the column, he added, "I keep bumping into that silly quotation attributed to me that says 640K of memory is enough. There's never a citation; the quotation just floats like a rumor, repeated again and again.""
FWIW the designers didn't want to use the 8088, but for cost reasons they had to go for a CPU with an 8 bit data bus. The 8088 was a version of the 8086 that was designed for that purpose. But the 68008, which was the 8 bit bus version of the 68000 wasn't available in 1981.
Nobody really expected the original PC to be the basis for the standard, it was only meant to compete with the Apple 2 and sell a few thousand & maybe stick a terminal card in so you can hook it up to your IBM mainframe.
By 1985 Microsoft were selling a card for the PC that allowed you to expand it beyond 640k, so if someone made up that quote after 1985 it makes no sense whatsoever