God would have to actually appear and take all the speculation out of it, first of all. I have no respect for this hide-n-seek game. Either come out and show yourself, or you're not real. It's been my challenge to God since I stopped believing, same with billions of others through the ages I would imagine.
If God did finally get the stones to show up, my reaction would depend on what he said. What's he asking for? Is he showing up to say "I made this world and you must worship me for it?" That's blackmail. I didn't ask you to make it, and now I have to spend my life making certain chants and incantations and be your dancing monkey? If he says "worship me or I'll send you to eternal torturous damnation in fiery hell" I guess I would worship him, but then I'd be no more than a prisoner in a concentration camp. If he says "live in peace and harmony with your fellow humans, take care of the planet I gave you, and treat all life with respect and dignity" I'd comply with that in an instant.
Of course I already try to comply with that idea, sans any appearance from the non-existent UberDude, so I don't know what he'd really be adding.
It's a pretty broad question, one that I don't ever expect to have to face.
God had already written down how and when he will "show up".
He was more present/directly involved in earlier times, but it didn't do any good because we had no reference and were not yet prepared -but it was necessary to begin that which prepares us.
All that mankind has been learning is essentially about God (everything is essentially God) -as the things of God are apparent in what was made. He is simply less obvious at present.
All of our greater problems and issues require God -and that needed to be made clear.
Once it is clear, God will answer them and we will understand that he is necessary -and we will understand that he is who he says he is.
Christ will return just before we destroy all life on Earth -so it can be shown to be the result without him.
Then the kingdoms of the world will become his -and he will enforce and teach peace.
The armies of the Earth gathered in Megiddo to fight each other will turn to fight him at his return -and he will destroy them.
Then there will be great changes on Earth.
Mat 24:21 For
then shall be great tribulation, such as was not since the beginning of the world to this time, no, nor ever shall be.
Mat 24:22 And
except those days should be shortened, there should no flesh be saved: but for the elect's sake those days shall be shortened.
Zec 14:3
Then shall the LORD go forth, and fight against those nations, as when he fought in the day of battle.
Zec 14:4
And his feet shall stand in that day upon the mount of Olives, which is before Jerusalem on the east, and the mount of Olives shall cleave in the midst thereof toward the east and toward the west, and there shall be a very great valley; and half of the mountain shall remove toward the north, and half of it toward the south.
Zec 14:12
And this shall be the plague wherewith the LORD will smite all the people that have fought against Jerusalem; Their flesh shall consume away while they stand upon their feet, and their eyes shall consume away in their holes, and their tongue shall consume away in their mouth.
Zec 14:16 And it shall come to pass, that every one that is left of all the nations which came against Jerusalem shall even go up from year to year to worship the King, the LORD of hosts, and to keep the feast of tabernacles.
Mic 4:1 But
in the last days it shall come to pass, that the mountain of the house of the LORD shall be established in the top of the mountains, and it shall be exalted above the hills; and people shall flow unto it.
Mic 4:2 And
many nations shall come, and say, Come, and let us go up to the mountain of the LORD, and to the house of the God of Jacob; and he will teach us of his ways, and we will walk in his paths: for the law shall go forth of Zion, and the word of the LORD from Jerusalem.
Mic 4:3 And
he shall judge among many people, and rebuke strong nations afar off; and they shall beat their swords into plowshares, and their spears into pruninghooks: nation shall not lift up a sword against nation, neither shall they learn war any more.
Mic 4:4 But they shall sit every man under his vine and under his fig tree; and none shall make them afraid: for the mouth of the LORD of hosts hath spoken it.