You haven't linked to the full source of the article but from the snippet it doesn't provide any evidence that IM/text messaging is replacing email and hence email is 'old', it just states that Korean kids would prefer to use IM/text messaging to chat and rarely use email.
There is nothing new or revolutionary about this and this is exactly how things were in 1999 - IM/text messaging does not replace email or post, it replaces phone calls. Instant messaging, text messaging and phone calls are all for either short individual messages or for a series of short messages that make a conversation in 'real time'. Email has never done this, or tried to do this. Email replaces post - if you want to send a longer piece of communication you use an email or a letter, as opposed to a phone call or an IM/text message for a short message or conversation.
The article wrote:
even email seems like an incredibly slow way to communicate
How can email be slow? It is instant, especially when compared to a letter. The fact that it may take a while to write an email compared to a text message/instant message simply relates to the length of the message, and the fact that email has never been designed to have a real time conversation with, even if the near instant nature of email allows this.
Text messages are so much more convenient than a phone call and much more accessible than email.
I'm not sure what phones are like in the US at the moment, but the last two mobiles I've owned have received/sent email and store the messages in the same inbox as the text messages if you want - so email is no less accessible than a text message.
To join in the 'I use <bla> because <bla>' posts, I use everything when the use is correct.
- Instant messaging when you want to communicate in real time using a PC (eg. talking to work colleagues in different locations)
- Email when I need to send a longer message, or have an easy to track stored record of the messages. For example communicating with clients regarding technical issues.
- Text messaging when I need to send a short message to someone, or have a conversation when a phone call would not be appropriate (a text is much more discrete than a phone call, and doesn't demand the person stops what he/she is doing. It is often also cheaper, especially mobile -> mobile).
- Phone when I need to have a conversation in real time.
- Post when a hard copy is required.
None of the above is revolutionary, and none of the above has really changed in the last few years, other than the fact more people have access to the newer technologies.