Chupa Chupa said it best in this thread "8GB is doable but 16GB is more comfortable."
Bottom line is that I personally wouldn't go below 8GB right now in 2017 if I was buying new. I wouldn't spend over grand on a laptop or desktop in mid 2017 with less than 16GB of memory. If the money was that big of a deal to me and I had to worry over the possibility of flushing down $180 for something I am planning on using every day for at least 3 years then I'd probably wouldn't be dropping that much money on an Apple laptop as a college student to begin with.
You're asking if I think in the year 2020 will 8GB be obsolete? I think obsolete is a strong word but you might run into issues depending on what you are doing and if your usage changes at all. Thats just 3 years. The OP might want to use this computer in 2022(5 years) or beyond. 5 years isn't some ridiculous age for a laptop. I have a 5 year old Macbook Air right now and I'm sure as heck glad I opted for 8 GB over 4 GB.
I just know I've seen a lot more people complain about not upgrading ram than the other way around.
skaertus and
throAU already confirm this on page 1. I'm sure I can find a lot more personal andoctes like that over someone complaining that they got too much ram.
ZapNZs had a very good post on this subject as well
https://forums.macrumors.com/threads/do-i-need-more-ram-a-few-days-to-decide.2030300/#post-24266029
"I look at non-upgradable hard drives & RAM on a computer one may keep for 5-10 years the same way I look at gun safes (I used to sell safes): with no way to predict the future needs/preferences, the premium for going slightly bigger is usually preferable over the regret of going smaller. In 2007, the standard RAM on a MacBook Pro was 2GB; in 2011 it was 4GB; as of 2016 it is 8GB. Even today, with the current version of OS X, the difference between 4GB and 8GB for moderate use is often pretty significant. Maybe 8GB will work great in 2021, aided by such a fast SSD, but I feel 16GB is a safer bet for a large investment. And unlike the days when people were saying 4GB of RAM is all one could ever need, we can't upgrade the RAM very easily (as doing so carries significant risks and will obviously void the warranty.) That's just my personal opinion."