Bkvader,.
I hate to tell you this, but there is absolutely no doubt in my mind that this song is indeed about heaven. There are bible verses that talk about indeed being "foreigners in the land".
Also, 1 Corinthians 13: 12 says "Now we see but a poor reflection as in a mirror; then we shall see face to face. Now I know in part; then I shall know fully, even as I am fully known." Sounds a lot like the lines in the first verse.
There are multiple times in the song where he describes a place that sounds a lot like heaven, for example, "...the land... where they'll be no pain or tears anymore" and "the city that endures forever."
This song is not about something bigger than heaven; this song is about heaven, which actually is bigger than pretty much any other subject. Your line at the end of your statement:.
"I say get attached to all that you can in this life because after this there will be no music."
Is very ironic because that is the exact opposite of what the song is about.