Using the Greek translation
The word kosmos refers to the universe or the whole of creation.
kosmos is the word the Apostle John used in 1 John 2:2
2 He is the propitiation for our sins, and not for ours only but also for the sins of the whole world = kosmos or the universe or the whole of creation
So John is saying not just the saved, but Jesus died for EVERYONE!
Whatever was intended by God to be covered by Christ's offering can neither die nor be destroyed. If either could, then His offering didn't achieve what God had intended it to achieve. But we know it wasn't a failure and perfectly achieved what it was intended for because God had fully accepted it - hence Christ's title of Saviour. It can't be both ways: that He is the Saviour and yet all covered by it don't become saved - that would be a logical contradiction of the highest order.
This current "kosmos" (world) is to be destroyed by God but two are mentioned in the Bible not one: this one, along with its unsaved, which will be destroyed, and a new one with those saved by Christ who will inhabit it - both eternal. Christ is the Saviour and as Saviour, whatever was covered by His offering, can neither die nor be destroyed but must live/exist eternally.
Now, I cannot speak to what the new one will be like - it might just be Christ together with His saved in the air (see 1 Th 4:17 below), and not a world as we know it today.
[2Pe 3:7, 10-12 KJV]
7 But the heavens and the earth, which are now, by the same word are kept in store,
reserved unto fire against the day of judgment and perdition of ungodly men. ...
10 But the day of the Lord will come as a thief in the night;
in the which the heavens shall pass away with a great noise, and the elements shall melt with fervent heat, the earth also and the works that are therein shall be burned up.
11 [Seeing] then [that] all these things shall be dissolved, what manner [of persons] ought ye to be in [all] holy conversation and godliness,
12
Looking for and hasting unto the coming of the day of God, wherein the heavens being on fire shall be dissolved, and the elements shall melt with fervent heat?
[1Th 4:17 KJV]
17 Then we which are alive [and] remain shall be caught up together with them in the clouds,
to meet the Lord in the air: and so shall we ever be with the Lord.
[Mar 10:30 KJV]
30 But he shall receive an hundredfold now in this time, houses, and brethren, and sisters, and mothers, and children, and lands, with persecutions;
and in the world to come eternal life.
[Luk 18:30 KJV]
30 Who shall not receive manifold more in this present time,
and in the world to come life everlasting.
[Heb 2:5 KJV]
5 For unto the angels hath he not put in subjection
the world to come, whereof we speak.
[Heb 6:5 KJV]
5 And have tasted the good word of God,
and the powers of the world to come,