I don't think any movie will ever make as much money. Gone With the Wind had a 3 year long run and people had less ways of entertainment back then. The Force Awakens still has a chance to overtake Phantom Menace though, that's a more realistic and meaningful feat.

Less entertainment methods but also a much lower and much poorer population. There's 186M more people now with a total of 318M living 10-15 years longer. There was also a lot less theatres so it was less accessible than nowadays.

I think it will crack the Top 10 but not the Top 5.

It was also released 7 times, as recent as last year, so it has had every advantage of every generation.

It's hard to believe that another film will see such fortuitious circumstances.

I don't think anyone is expecting it to become #1 all time adjusted. This will be it's first run after all. Even the first Star Wars didn't get to be #2 on the list from one theatrical run alone. However it's going to be going higher on the list than all but a very select few movies and to be #21 after only 3 weeks is amazing. The question now will be how long it can keep it up. While it obviously won't be like many of the movies on the list that ran for years in their first runs, or even Titanic that was #1 for 15 weeks streight. It's also not just going to completely fizzle out like many movies these days do after huge opening weekends.

Boxofficemojo shows 2 re-releases with minor grossings in 1989 and 1998. I'm assuming these were very limited while the ones not mentioned were in a very few select theatres. The 1998 re-release was in 214 theatres. Very different situation from the Star Wars re-releases which released in 1982 and 1997 in 1070 and 2104 theatres respectively.

It can however many re-releases, that won't matter since re-releases don't make a lot of money (unless they re-release in in 20 years' time as a wide release but even then...).

There were releases in 1939, 1942, 1947, 1954, 1961, 1967, 1971, 1974, 1989, 1998, 2013, and 2014: https://en.wikipedia.org/wiki/Gone_with_the_Wind_(film)#Later_releases

Oh indeed most limited rerelease of the classics these days do little but there is a lot of room between The Star Wars special editions run and Gone with the Winds 75th aniversary depeding on how far it get's now, a rerelease down the line could bump it up a few spots on the list, but until we are much closer to seeing just how much it does now there is no point predicting what future rereleases may or may not add.

No mention of the theatre count or grossings so it's kinda pointless to discuss re-releases (it could be a handful of theatres for all we know). The 2 that we have data of show a low amount.

Btw, the original Star Wars has releases in 1977, 1978, 1979, 1981, 1982 and 1997.

https://en.m.wikipedia.org/w/index.php?title=List_of_highest-grossing_films&redirect=no#Timeline_of_highest-grossing_films

Go to the section timeline of highest grossing films. You'll see what up to point it got passed by the sound of music. Plus how much it had when it retook the title if highest grossing movie in the US and compare that with the total they show on box office mojo and see that it wasn't all in its first release. 

Or look at Snow White and the Seven Dwarfs they even mention it on box office mojo how it made most of its adjusted gross after 1980.