IF a Christian REALLY believes the Bible is the infallible words of God, then the "old fashioned language" is not an issue at all. Sure, the King James Bible has some words that are older or have different meanings than we may be familiar with.
But people are learning new vocabulary or new meanings to English words all the time in any field of study, be it sports, biology, the sciences, mathematics, medicine or just about anything imaginable. If you are interested in something, you learn the meaning of the words that are found in this field of interest. Even when you start using the computer we have to learn some new words or different meanings to words we already knew - Words like "mouse", IPad, "Kindle", Office, Word, "paste".
Do we need to "update" the language of the Bible?
God knew that languages would change over time and that His pure words, as found only in the King James Bible, would sound slightly “strange, different and old fashioned”, but this is a good thing. When people read out of the King James Bible we are immediately struck by the fact that it reads like NO OTHER BOOK on this earth. It is an OLD Book that has been around for a good long time, and it speaks God’s eternal truths to us like no other book or Bible on this earth. The very way it is written sticks in the mind and makes you think about what it is saying the way the watered down and dumbed down modern versions do not.
Most modern versions have more the taste of cardboard than of the sweet honey of God’s pure words as found in the King James Bible. And it is the ONLY one seriously believed by thousands even today to be the complete, inspired and 100% true words of the living God.