Okay, I'm just spit-balling here.
The last SPS figures we got for Tear and Her were:
YouTube counts towards RIAA certification.
YouTube US Streams from release until 8/12 for DNA: 54,788,337
YouTube US Streams from release until 8/12 for MIC Drop: 37,924,252
If we break those into album-equivalent, DNA earns Her 36,525.558 additional albums. MIC Drop earns Her 25,282.834 albums.
Using the last-known SPS figures, that would be a total SPS of 416,808.
Comparing the SPS from week to week, it looks like Her climbs about 5,000 each week. Using the last few weeks as an example, DNA and MIC Drop are pulling in 905 album-equivalent streams from YouTube. For ease, let's say that Her gains about 5,900 SPS per week.
Approximately 84,000 album sales needed, gaining 5,900 a week: Gold in about 14-15 weeks?
Take all of this with a grain of salt and feel free to nitpick my math and methodology. I'm also not 100% sure that MIC Drop counts towards RIAA certification. But if DNA does, wouldn't it make sense that MIC Drop would? Also, maybe Serendipity counts? I can't find Serendipity's numbers on BTS' Artist Insight page.
Now for Tear.
YouTube US Streams from release until 8/12 for Fake Love: 36,603,493.
Album-equivalent would be 24,402.32. That would be an SPS of 352,402.
Tear will be harder to guesstimate because it varies a lot between weeks. The last four weeks, it's gained 12,000 SPS, 12,000 SPS, 7,000 SPS, and 9,000 SPS. I think I'm going to go conservative and say it gains around 8,000 SPS per week.
YouTube views are also hard to gauge. In the last two weeks, it gained 949 albums and then 839 albums. I'll say 800. That would be 8,800 SPS per week.
147,600 SPS needed, gaining 8,800 a week: maybe somewhere around 16-17 more weeks for Gold?
Once again, perhaps Singularity counts, but I don't know the US streams to estimate how much it's added.
I do think sales for Her and Tear will spike when Answer is released. I think a lot of people will go to buy Answer and pick up Tear and Her, too. We'll see.
And so ends my completely novice research and math.