No, it won't. BTC is BTC and all other altcoins are well "alt"-coins, they are essentially a different currency. It's the same thing as there are USD and GBP, but neither of them dilutes either of them.
USD and GBP are both currencies created by their countries' respective governments and banks. They are only supposed to be used in the country that created them, or other places whose governments decide to make them legal tender.
BTC and altcoins are entirely free and can be spent or accepted by anyone in the world for anything.
BTC was created for a specific purpose - to be a "Peer-to-peer Electronic Cash System". I would argue that the status of Bitcoin makes it almost impossible to be displaced or threatened by a clone.
Because doing better than Bitcoin with a clone is extremely difficult, it requires coins which have different purposes or people believe to do the purpose of Bitcoin better. Therefore, these alts can never "dilute" the limit, because they are not the same thing.