According to Preterism has Jesus already delivered the kingdom to God? 1 Corinthians 15:22-25 (ESV)
  For as in Adam all die, so also in Christ shall all be made alive. But each in his own order: Christ the firstfruits, then at his coming those who belong to Christ. Then comes the end, when he delivers the kingdom to God the Father after destroying every rule and every authority and power. For he must reign until he has put all his enemies under his feet.  


I assume this refers to when Christ destroyed death, the last enemy, which is in the past.

So do Preterists say that after 70AD "the end" came and Jesus ceased to reign so that God might be all in all?
Preterism is the view that the Biblical prophecies concerning the end times have already been fulfilled. I understand they get this conclusion from such verses as Heb 2v14 where the Devil is destroyed. Here we might say that the contract is signed but the resulting possession not fully entered into. Also, "this generation" Mat 24v34 could be the people who see these things.
When "you" [Jews] see these things [some time in the future], the generation who sees these things, will not pass away until all these things take place.
"These things" may take  place 2000+ years hence, but when they do take place they will occur with such rapidity that one generation will witness them all.