C4K said:
Did this decision to introduce new versions start in 1611 or some time earlier or later?

Well, actually the first English version was a translation from the Latin Vulgate by Wycliffe in 1385 or so. When Tyndale translated the first English Bible from the original languages (he didn't actually complete the OT before he was executed) in 1526 (NT) he also used Wycliffe's work along with Luther's German translation. The KJV is simply a revision of Tyndale's work - considering all of the other revisions of Tyndale's work at the time. Their intent was to come up with a Bible which combined the best features of the existing Bibles, and they did a pretty good job of it. (Not to say that it was much different than the Bibles which preceded it.)
But the point is that the KJV was not really a new translation. You'd have to consider all of the revisions of the KJV since 1611 to be different translations - which they obviously are not.
Once you change the spelling differences in Tyndale's work, it is 95% the same. I've compared a few passages. They changed it about as much as the changes to the RSV to produce the ESV.
I chose the following well-known Bible texts at random:
Tyndale -
John 3:16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
KJV (today) -
John 3:16 For God so loveth the worlde yt he hath geven his only sonne that none that beleve in him shuld perisshe: but shuld have everlastinge lyfe.
Wycliffe -
John 3:16 For God louede so the world, that he yaf his `oon bigetun sone, that ech man that bileueth in him perische not, but haue euerlastynge lijf.
Tyndale -
Galatians 2:20 I am crucified with Christ: nevertheless I live; yet not I, but Christ liveth in me: and the life which I now live in the flesh I live by the faith of the Son of God, who loved me, and gave himself for me.
KJV (today) -
Galatians 2:20I am crucified with Christ. I live verely: yet now not I but Christ liveth in me. For ye lyfe which I now live in ye flesshe I live by the fayth of ye sonne of God which loved me and gave him selne for me.
WYcliffe -
Galatians 2:20 and Y am fitchid to the crosse, that Y lyue to God with Crist. 20 And now lyue not Y, but Crist lyueth in me. But that Y lyue now in fleisch, Y lyue in the feith of Goddis sone, that louede me, and yaf hym silf for me.
None of the above properly translate the perfect passive tense. It should be
"I have been crucified with Christ..."
Tyndale -
2 Corinthians 5:17 Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new.
KJV (today) -
2 Corinthians 5:17 Therfore yf eny man be in Christ he is a newe creature. Olde thynges are passed awaye beholde all thinges are be come newe.
WYcliffe -
2 Corinthians 5:17 Therfor if ony newe creature is in Crist, the elde thingis ben passid.
Oops. WYcliffe skipped something!
Tyndale -
Acts 1:8 But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth.
KJV (today) -
Acts 1:8 but ye shall receave power of the holy goost which shall come on you. And ye shall be witnesses vnto me in Ierusalem and in all Iewrye and in Samary and even vnto the worldes ende.
Wycliffe -
Acts 1:8 but ye schulen take the vertu of the Hooli Goost comynge fro aboue in to you, and ye schulen be my witnessis in Jerusalem, and in al Judee, and Samarie, and to the vtmeste of the erthe.
Tyndale -
Ephesians 2:8, 9 For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast.
KJV (today) -
Ephesians 2:8, 9 For by grace are ye made safe thorowe fayth and that not of youre selves. For it is the gyfte of God and commeth not of workes lest eny man shuld bost him silfe.
Wycliffe -
Ephesians 2:8, 9 For bi grace ye ben sauyd bi feith, and this not of you; for it is the yifte of God, not of werkis, that no man haue glorie.
Again, Tyndale and the KJV mishandle the perfect passive tense. WYcliffe did OK.
ANyway, I see a few differences between Tyndale's work and the KJV, but not much - once you discount the spelling.
FA