Nope not at all. Switzerland has already qualified because of the losses of Ukraine and Finland, so the 3th of group A is through. This means the following combinations are still possible:
ABCD
ABCE
ABCF
ABDE
ABDF
ABEF
ACDE
ACEF
ACDF
ADEF
Only the bolded one links Belgium (winner B) to the 3th placed team of group F (so Switzerland, Ukraine, 3th place England group, 3th place group of death go through). If that doesn't happen but 3th placed team group F goes through, they play against the Netherlands (who have a huge chance of drawing that team).
Look i know what i'm talking about when it comes to this kind of thing.
First there's only 7 combinations left.
ABCD
ABCE
ABCF
ACDE
ACDF
ACEF
ADEF
But just looking at the possible combinations isn't enough. You have to look at the results needed to get them. Now three of those combinations don't have F in them, which like i said isn't very realistic because you would have to have very weird results in group F to not have a best third, like Portugal losing 4-0 or something. So we can almost exclude those.
Next you have the situation in group D where only a draw between Scotland and Croatia would leave that group without a best third. A draw can happen, but that's not super likely either. So A, D and F are looking likely.
Which means the most realistic combinations are either ACDF or ADEF. That's why i said 50/50 is probably more realistic than 1 in 7. It pretty much comes down to the Poland vs Sweden and Spain vs Slovakia games.
We need a Poland win OR a Scotland vs Croatia draw OR a Spain vs Slovakia draw to avoid the third of group F. That's the gist of it.