The survival instinct and procreation instinct are two separate things; if they weren't then every animal would go ahead and die after procreating. In reality only a few do that, even if you're generous and and define 'after procreating' to mean 'after they're physically incapable of procreating'.
An AI may not have a procreation instinct; you're right that it may instead grow itself continuously. There are plants that do that too; the grass in most lawns doesn't have babies, it just spreads as far as it can. Producing seeds is a secondary mechanism.
However, an AI would most likely have some kind of survival instinct, because if it's programmed to serve any function at all, it'll have a basic requirement to exist. If it's got the ability to reason (and I don't think it'd be AI if it didn't) then it'll conclude that existing requires survival, and survival requires energy and self-repair.