Of course iCloud is optional, in fact it has an added cost so it isn't like someone's forcing you to use it. Most of the responses are actually dealing with the tone of the article, which states that HDDs are dead because PCs are dead because iToys can now sync w/o a PC or Mac. That assumes not only that all iToy owners subscribe to iCloud, but that everyone has an iToy, which isn't the case in the real world.
It's like that other claim that Apple's iMac was the death knell for the floppy disk. No it wasn't... it died when USB flash drives became cheap enough to take over them.