What the Bible says about Second Aorist Tense
(From Forerunner Commentary)
Because the word translated as "come" here is not in the Greek future tense, but in the "second aorist" tense, many modern Bible translations correctly render this as "Let your kingdom come" or "May your Kingdom come," giving the solid idea of a future certainty. God's Kingdom will come. Jesus knew that it would come, but He wants His brothers and sisters to pray relentlessly for its coming, that it will come as soon as possible!