No, unbelievers do not inherit the kingdom. Doesn't matter if they used to or never did believe. Unbelievers go to the left into the fire, not to the right into the kingdom.
Freegrace doctrine says unbelievers WILL go into the kingdom. That's so blasphemous it's hardly worth the attention except that so many in the church now believe that's true.
And traditional once saved always saved doctrine (the 'P' in TULIP) says you can't know if you're truly saved until you get to the end.
And these are supposed to be doctrines of eternal security and assurance.