So, I think the second Stormlight arc (books 6 to 10) will take place at least seventy years after the ending of Stormlight 5.
Reasons:
then we have
which makes this the right timeline
Now the trickier part. Brandon said a few times that the core cosmere sequence goes: Dragonsteel - Mistborn Trilogy 1 - Stormlight Arc 1 - Mistborn T2 - Stormlight A2 - Mistborn T3. Unfortunately, I can't find any quote. I think he said it in one of the Waygate foundation videos, but I'm not entirely sure. I hope there's someone who can confirm this.
So, seventy five years between Mistborn Adventures and Mistborn T2 with Way of Kings taking place before Alloy of Law a Stormlight Arc 2 after Mistborn T2. That would be cool.
Now some problems:
Eighty years, that's no small gap. On the other hand, eighty years compared to three hundred between HoA and Aol...
But a few years ago, Brandon was toying with the idea of another Kaladin flashback book. Maybe it was because there is such a long gap?
Anyway, That's all I have. Apologies for my English.