The final four of the Scottish Cup is set, so I will give my subjective outlook on which sides I expect to end up in Europe next season. There are 3 more matches before the split (where the top-half sides only play top-half sides). At the split, I will get more quantitative.
Celtic
Chance of playing in Europe: 99.99%
Path to Europe: Not have a complete collapse in the league, or have a complete collapse and not have the teams below them have a spectacular rise, or win the Scottish Cup. Basically, they can still mathematically finish as low as sixth, but that's not going to happen. Fivethirtyeight gives them a 96% chance to win the league again, and being passed by three or four other clubs is almost out of the question.
How happy we should be if they are in Europe: Very. If Rangers pulls off the 4% upset, they might add enough quality for the Champions League, but Celtic is clearly the class of the nation still.
Managerial Outlook: Last year I said, "...it's not unrealistic to see Brendan Rogers being lured away." He was! But Neil Lennon is also very good. Hopefully they keep him, but
Rangers
Chance of playing in Europe: 95%
Path to Europe: Not have a collapse in the league. They're second and have been playing well. It would be a disappointment to end up third, a big disappointment to end up fourth, and even that would be enough depending on who wins the Cup.
How happy we should be if they are in Europe: Very. They are the only side other than Celtic I can see making it into the knockout stages.
Managerial Outlook: It doesn't seem time for Brendan Rogers to be lured away yet.
Aberdeen
Chance of playing in Europe: 90%
Path to Europe: Hold on in third, win the Cup, or drop to fourth and have Celtic win the Cup. (Or drop to fourth and have Hearts move up to third and win the Cup.)
How happy we should be if they are in Europe: Quite. They have consistently had decent European results, stopped only by running up against an EPL side (who they almost beat).
Managerial Outlook: If Derek McInnes didn't leave for Rangers, I think he's there for a while. He would like to hoist a trophy or two.
Kilmarnock
Chance of playing in Europe: 40%
Path to Europe: Stay in fourth and have Celtic and Aberdeen win the Cup, or move up.
How happy we should be if they are in Europe: Not. They are a classic Scottish side who overachieves domestically, but doesn't have the funds to compete in Europe.
Managerial Outlook: Clarke seems like a great manager; maybe he will take over a bigger Scottish club.
Hearts
Chance of playing in Europe: 55%
Path to Europe: Win the Cup, move up to fourth and have Celtic or Aberdeen win the Cup, or move up to third. They have had some nice results, so moving up to fourth or winning the Cup can't be ruled out.
How happy we should be if they are in Europe: Somewhat. They have the resources and they may be willing to spend a little with their stadium renovations done.
Managerial Outlook: Good. Levein is doing a good job, and doesn't seem to have ambitions elsewhere.
Everybody Else
Chance of playing in Europe: 25%
Path to Europe: Hibs, Motherwell, St. Johnstone and Livingston are all alive for the sixth spot at the split. Then they could mathematically make it into the top three or four. Maybe 25% is high, but Hibs could make some noise. Inverness CT doesn't have much chance to win the Cup out of the second tier, but it has happened before.
How happy we should be if they are in Europe: Not, except maybe Hibs.
Managerial Outlook: Mixed.