Martin Scott is helpfully provocative on the language of kingdom:

The time has come to bring an end to kingdom language. The time has come to listen carefully to the Gospel story, especially as John tells it (Jn 15:12-17), to find a real radical heart which places shared community rather than individual values at the centre.

What we need today is both an expression of Christian faith and a world order based on friends being in relationship (Jn 15:15) rather than servants of a glorious king; on community rather than kingdom; on justice, love and peace rather than kingdom, power and glory.

However, the first step is talking about this at all. A Christianity of individual salvation alone would not be recognised by its founder.