And in general, how the Kingdom is now offered to the Gentile, and should the Gentiles in general refuse it as the Jews have, then the offer of the Kingdom to the Gentiles, in general, will be removed.
Again, this is not what Paul is saying. Notice the context:
Rom 11:13
For I speak to you Gentiles; inasmuch as I am an apostle to the Gentiles, I magnify my ministry,
Rom 11:14
if by any means I may provoke to jealousy those who are my flesh and save some of them.
Rom 11:15
For if their being cast away is the reconciling of the world, what will their acceptance be but life from the dead?
Rom 11:16 For if the firstfruit is holy, the lump is also holy; and
if the root is holy, so are the branches. (NKJV)
And then:
Rom 11:17 And
if some of the branches were broken off,
and you, being a wild olive tree, were grafted in among them, and with them became a partaker of the root and fatness of the olive tree,
Rom 11:18 do not boast against the branches. But if you do boast, remember that you do not support the root, but the root supports you.
Rom 11:19 You will say then, "Branches were broken off that I might be grafted in."
Rom 11:20 Well said.
Because of unbelief they were broken off, and you stand by faith.
Do not be haughty, but fear.
Rom 11:21
For if God did not spare the natural branches, He may not spare you either.
Rom 11:22 Therefore consider the goodness and severity of God: on those who fell, severity;
but toward you, goodness, if you continue in His goodness. Otherwise you also will be cut off.
Rom 11:23 And they also,
if they do not continue in unbelief, will be grafted in, for God is able to graft them in again.
Rom 11:24
For if you were cut out of the olive tree which is wild by nature, and were grafted contrary to nature into a cultivated olive tree, how much more will these, who are natural branches, be grafted into their own olive tree? (NKJV)
Do you see it now?
God removed the unbelieving branches in order to graft in those Gentiles who do believe, those Gentiles which were
first removed from the wild olive tree. This means they were
first removed from the world and its belief systems on the basis of their faith in God and grafted in to the cultivated olive tree where the unbelieving Jews had been removed.
The analogy Paul uses is this: useless branches in a cultivated olive tree, that is, branches which should produce fruit but don't, are removed and branches which do produce fruit are grafted in. Yet, not only do these grafted in branches produce fruit, they are from the wild olive tree, not another cultivated one. It is this act of cultivating which keeps the tree fruitful. God was bringing in Gentiles to keep his kingdom fruitful.
Paul is warning those Gentiles who think themselves better than the natural branches to be careful and fear God (something Jesus says to do also) because He can remove those who stop believing and re-graft in those who begin believing again.