A lot of discussion in last few days about what teams go where, particularly since Manchester City and Liverpool both could end up outside the top 4 in the EPL.
Some basic rules:
(1) There cannot be more than 5 clubs from one league ('domestic association') in the CL.
(2) The CL winner always qualifies directly for the next year's CL Group Stage.
(3) The EL winner always qualifies AT LEAST for the Play-Off Round of the CL.
(4) You work your way down from the top: that is, there is always a place in the CL Group Stage for the CL winner, and for the top three clubs from the EPL, from Spain, from Germany. If one team has qualified for the group stage by both domestic placing and winning the CL, then the EL Winner takes that 'empty' CL Group Stage spot.
(5) Places get redistributed within an association--not between them. In other words, a league entitled to three EL places will get three EL places--the redistribution rules determine which teams from that league fill those three places, and where those places are within the competition--qualifying rounds, play-off round, group stage.
Some basic observations:
(1) Of the four CL semifinalists, three (Bayern, Madrid, Atleti) have already qualified for the group stage of the CL. One (Man City) has not.
(2) Of the four EL semifinalists, based on domestic performance, one (Shaktar) is likely to qualify for the CL 3rd qualifying round; one (Liverpool) may not qualify for Europe at all; one (Sevilla) will qualify for the EL, either for the group round as Copa del Rey winners or a qualifying round, as 7th place finisher, if Barca defeat them in the Cup Final; and one (Villarreal) has qualified for the CL playoff round.
Now, putting this all together:
If Sevilla, Villarreal, or Shaktar win the Europa League, they go into the CL Group Stage, if anyone other than Manchester City wins the Champions League.
If Manchester City win the Champions League and finish in third place in the EPL, the Europa League winner goes directly into the Group Stage.
If Manchester City win the Champions League and finish in fourth place in the EPL, the Europa League winner goes into the Play-Off Round of the CL, NOT directly to the Group Stage. This is because Man City would only have qualified for the Play-Off round themselves through domestic performance; they go into the Group Stage as CL Winners.
A potentially really complicated scenario:
If Liverpool win the EL, and Manchester City win the CL, but both finish in fifth place in the EPL or below, England would have 6 teams in the CL, and they are only allowed 5. This is resolved by the fourth-placed EPL team being removed from the CL and put into the Europa League Group Stage, NOT the Champions League Play-Off Round.
For example, say the following happens:
EPL first three: Leicester, Tottenham, Arsenal (order doesn't matter)
EPL next four: Manchester United, West Ham, Man City (CL winners), Liverpool (EL winners).
CL Group Stage: Leicester, Tottenham, Arsenal, Man City
CL Play-Off Round: Liverpool
EL: Three teams. Manchester United, as fourth place finisher (directly into EL group stage), West Ham, as fifth placed finisher (into EL Group Stage) and eighth-placed finisher (Southampton?) into the third EL qualifying round. That's as long as Manchester United win the FA Cup. If instead Crystal Palace take it, then they and Manchester United would get into the Group Stage, West Ham would go into the third qualifying round, and Southampton would be knocked out of Europe.
If Spanish clubs win both the CL and EL, the situation is also complex, depending on whether the team winning the EL would have qualified for the Champions League anyway.
(1) Villarreal win the EL. Then, Spain would have four teams in the CL, and all would enter directly into the group stage.
The Europa League teams would be teams 5-7 in La Liga (Athletic Club, Celta, and Sevilla, at present). Athletic would go directly into the group stage; if Barcelona win the Copa del Rey final, Celta would go into the group stage and Sevilla into the third qualifying round.
Should Sevilla win the Copa final, then they and Athletic would go into the group stage and Celta would play in the third qualifying round.
(2) Sevilla win the EL. Now, Spain gets five teams in the CL. The top three, and Sevilla as EL winners, would go into the group stage; Villarreal would go into the CL play-off round.
Spain are entitled to three berths in the Europa League, so this means teams #5,6 and 8 (Sevilla is likely to be #7) would go into the EL: #5 and #6 directly into the Europa League Group Stage, and #8 into the third qualifying round.