"HTTP calling abilities of LLMs" is not some magic, new feature that is deeply integrated into LLMs. It's just a tool call like everything else - i.e. you prompt the LLM to return a JSON object that conforms to a schema.
MCP is also doing this exact same thing. It's just a wrapper protocol that tries to take care of all the details so that we don't have to deal with a million custom protocols that all accomplish the same thing but are all incompatible.
What you are describing, "web api calling abilities were to improve" will not change anything. What sort of improvement are you thinking of? They can only get better at outputting json correctly, but that hasn't really been a problem for a long time now.
Either way, it wouldn't change anything, because MCP is a 100 other things which doesn't have anything to do with the llms using tools directly. You will never embed everything that MCP can do "into" the llm - that barely even makes sense to talk about. It's not just a wire protocol.