Just a thought about the scriptures you quoted in Rev. Gino.  I had noticed along time ago that in Rev. 5:9 where it says

"And they sang a new song saying...."   The use of the word "us" would infer that these are raptured saints.  But I also have a footnote in my King James Scofield Bible for Rev 5:9.  It says "Most early N.T. mss. omit "us" in v. 9 and read "them" or "they" instead of "us" and "we" in v. 10"  I don't know how a thing like that could get changed because it totally changes the picture, but it did.  I believe that the early church knew a lot more about what was going on then the scholars of today, simply from the "closer to the event" idea.  So, Now if you insert Us and Them, you have a group that is not comprised of those that were/are 'redeemed".

I have been reading a book about the Greatness of God by James MacDonald and in there he talks about the 4 living creatures that surround the throne and continually say "Holy, holy holy, Lord God Almighty, who was, and is and is to come."  Actually the scriptures says that they rest not day and night saying this over and over again.  Then I realized something significant in what you posted, you pointed out that the 24 elders and the 4 living creatures all sang a new song.  Do you see that.  The 4 living creatures are not now continually saying "holy, holy,holy....."  They are singing a new song.  Maybe the "Holy, holy, holy " is a song as well right now, and then something so important happens that the song changes.  Maybe it is because the "who was, and is, and is to come." is being completely fulfilled at that time so a new song begins to be sung?  Just a thought.