Edit: Spelling
Some of them, yes. A great many are not. Taking your "last year" to be poetic rather than literal: -gate is cliche, "meme" is totally a thing now, "my bad" has diffused into informal communication all over Anglophonia, lolcat-speak still has everybody's great-aunt snorting at her Facebook wall, texting acronyms are well-known to everyone, word truncation + s is on its way to becoming totes ubiqs, etc.
Not to mention you're using a pretty useless definition of "outdated" if it includes literally everything.
ding ding ding, you're starting to get it!
More seriously, language can be thought of as a middle ground between production of an external symbol as a realization of thought, and interpretation of that symbol in another mind.
Even using language adhering to the strictest of grammars, there can be room for misunderstanding in the mind of the interpreter as they will be decoding your symbol expressions through a lens of their own understanding. Adhering to the model you think best does not guarantee clarity of communication!
You adjust the production model you use in order to better suit the interpretation model your audience is using. If your use of language is skillful enough, you can even help the audience select from several competing language models in order to add nuance -- you can speak in a vernacular or in a formal mode.