I don't think btc fork can affect btc in any way. Forking btc means they are creating a entire new altcoin and I don't think the creation of a new altcoin will affect bitcoin in any way. The developers  fork bitcoin to make a coin which has  better features than bitcoin with less transaction fees, faster confirmation etc. But I think all these forked coins are less decentralized than bitcoin because these forked coins have got a team behind it.