> Without AMD, ...

Perhaps? I don't know enough to judge whether one of the other companies working on IA-32 compatible processors could plausibly have stepped in -

https://en.wikipedia.org/wiki/List_of_former_IA-32_compatibl...

It's true that most of those would have lacked the resources to replicate AMD's feat with AMD64. OTOH, AMD itself had to buy out NexGen to produce their K6. Without AMD and/or AMD64, there'd be plenty of larger players who might decide to fill the void.