It's the windows 10 refusenik risk. You can pay for a one year extension. I think this is "if you owe the bank 200 million the bank has a problem" stuff: if Microsoft really do stop issuing fixes for live attacks, that's a huge surface of the internet going zombie/rogue. Every national CERT worldwide will be asking Redmond to revisit the decision.

It's 40% or more of the global surface of Microsoft acquired risk.

Does this mean I will be able to buy an extremely cheap, fairly new, windows laptop and install linux on it?

Needs to be really cheap, My state pension wont cover a brand new one

My old T450 with arch installed is looking a bit sore these days

I abandoned Windows after Win 7, but I still have a box. Maybe I'll take the upgrade to 10 just to boost the numbers.