You really have very limited options, like the rest of us:
(1) Purchase a Windows laptop and transition away from Mac. This is something you do not want to do, is costly, time consuming and difficult.
(2) Purchase a pre-2016 MBP. You already have a 2012 and at this point, I doubt you will find any 2015 MBPs for which you would be able to purchase AppleCare. Personally, I have purchased second-hand Macs, but not unless it had AppleCare or was still within the time period to purchase AppleCare. 2015 MBPs, as much as I like them, are probably not your best choice.
(3) Repair your 2012 MBP. For $300, this is your best solution, You can run Mojave (the latest macOS) and you have all the ports and power you should need for college, unless you have specific engineering requirements not met by your MBP.
(4) Wait. You might be rewarded for your patience, even if you get a new Mac after school starts. Still you might need a chromebook or Windows ultrabook to get by until then, in which case, you might as well repair your MBP while you wait for a new MBP.
(5) Buy a MBA. It will not be the same experience as your 2012 MBP, but again, they are cost effective, offer a wide variety of ports (but only have TB2), provide excellent battery life (much better than current MBPs), and should be sufficient for your needs. Should you decide to upgrade, you could always sell it later--just as you could if you repaired your 2012 MBP and then upgraded to a newer MBP later.
(6) *Not Advised* Buy a 2017 MBP and gamble with your education. Before you do this, ask yourself: how long does it take Apple to fix the keyboard issue if a problem developed? (Answer: ~1week) How will I function in college without my MBP if a keyboard repair is needed? Please understand that replacing a keyboard takes more time than other repairs. My advice: Do yourself a favor and don't buy a product with a known critical problem. Without your keyboard, a MBP is useless, especially in college. The last thing you need is to have to be without your MBP for a week when papers are due so that Apple can repair it.
Realistically, even if Apple announces new hardware in September, it will be Oct/Nov before it is released. You really need to accept the fact that more than likely, you only have the above options. Many of us are in the same boat, whether it is needed for school or work.
How is it expensive, time consuming, and difficult to transition to Windows OS? I use both interchangeably and have for years - what's the big deal?