Speak English

It's interesting that you cite SMS. That's precisely an example of language adapting to a new medium where the old language is inadequate. The shortening of words (and even sentences) for SMS is a product of people trying to leave written messages in a manner that takes up as little text space as possible, hence reducing the cost of the SMS. Funnily enough this is actually a return of an older means of communication - that of telegraph abbreviations. Seriously - you compare SMS-speak to an old telegraph message and they are extraordinarily similar - and for the precise reason that both mediums encouraged the invention of strong abbreviations to reduce sending costs. And net-chat is probably the most obvious case for linguistic change. Now I'm not particularly into net-chat myself, but I do play a few online games (counterstrike et al) when I have too much free time, and a similar system of real-time typed communication is used. Net-chat abbreviations were invented because the conversation is going on 'in real time' - i.e. there are 2 people both typing to each other simultaneously. Shortening sentences into abbreviations allows the conversation to flow like a verbal conversation. Over time some of those abbreviations took on their own connotation, so that you could still communicate the literal meaning of the abbreviation by using the old english equivalent, but you'd be giving a slightly different connotation to the words. Again, if people can understand each other with the same level of expression then the language isn't deteriorating. Of course people who aren't familiar with new mediums are likely to be frustrated - if you warped a literate individual from 450AD into the 1950s I'd imagine the person from 450AD speaking an older version of the language would be similarly frustrated. But few people, if any, would choose to readopt the old language. Language will always adapt to its needs - if people are finding it easier to communicate in a certain way then there are usually good reasons for that. That's a different thing to literacy - the ability to communicate verbal language in a written form - but I see no reason why the changes you have mentioned would in any way hamper the verbal to written transition. If anything they would assist it, as those changes actually ORIGINATED in written communications - indicating an increase in literacy.