Upvote:2
It really does depend on your eschatological view. Futurists/Dispensationalist want to place passages like Luke 21:12 in the future before the second coming of Christ. However, Partial Preterists/Covenantalists as well as some Amillennialists (like myself) see passages Luke 21, Matthew 24 and Mark 13 as Jesus' prophecy of the destruction of the temple in 70 AD only (much qualification needed). It should also be noted that not all Amillennialists thinks this way. Many of them do see a typological fulfillment in 70 AD whereas the full and final fulfillment will be realized before the second coming of Christ in the future. Either way, a good book to read on the Partial Preterist/Amillennialist position is Sam Storms book called 'Kingdom Come'.
As far as the beating in synagogues thing, the apostles were actually beaten a few times in the book of Acts at 5:40 and 16:22-23 which in some sense can be seen as a regulatory fulfillment of Matthew 10:17 as well as Luke 21:12 even though they weren't always exactly in the synagogues themselves which is a detail I don't think has to be perfectly fulfilled. Jesus' point was that they were going to be persecuted for their devotion to Christ which is exactly what happen to them. I hope that helps. :)