I really don't want to tempt fate, but without getting ahead of things, results today across Europe have been good for United in terms of potential 2017-18 Champions League seedings.
As a result of Juventus, Liverpool and Real Madrid winning today, a few things are now clear:
Because Juventus and Real have both automatically qualified for the Champions League, the winners of the Europa League will get an automatic group stage place (without need for a playoff - this is not ordinarily guaranteed unless the Champions League winners have already qualified automatically, which they now have as a result of Juventus winning today);
Because Liverpool have now qualified for the CL, Arsenal are out, which helps United's rankings: Arsenal are above United in the UEFA coefficients, but Liverpool are not;
Because Juventus have now won Serie A, Napoli and Roma cannot leapfrog United in the rankings (what with the champions of the top eight leagues all getting top seeding regardless of their own individual rankings): as Juventus' ranking is already better than United's, this was a good result for United.
But the most important thing is this: as a result of those results, if United win the EL, they will be *second* seeds, not third seeds; United are now effectively ranked at worst 16th. If a team below United in the rankings like Roma or Napoli had won Serie A, they would have leapfrogged United, but that cannot now happen. The impact of that is huge. Before considering the league winning bonus, United are ranked by UEFA coefficient as 15th in Europe. A few teams have leapfrogged United as a result of being national champions (Monaco, Spartak, Shakhtar), but a few others have missed out on Champions League qualification entirely (Arsenal and Schalke). That puts United from 15th, down to 18th, then back up to 16th.
As it stands, the first seeds in next season's CL will be:
Real, Bayern, Juventus, Chelsea, Monaco, Spartak, Benfica, Shakhtar
And the second seeds will be:
Barcelona, Atletico Madrid, PSG, Dortmund, Sevilla (if they get through the playoff round), City, Porto.... and, in 16th place, if they win the EL, United.
Compared to the third seeds, there's a huge benefit in being second seeds. The third seeds look like being a selection from:
Napoli, Spurs, Basel, Dynamo Kiev, Ajax, Olympiakos, Galatasaray, Anderlecht, Liverpool, Roma and Celtic (unless a few of these miss out).
There's definitely a benefit in being second seeds and drawing a side like Anderlecht or Basel, and being a third seed and drawing a side like Barcelona or Dortmund. That'll be the fate of Spurs, unless somehow Napoli and Sevilla don't make the group stage. Liverpool could be even worse and be fourth seeds, although they will likely slip in as third seeds if they make it.
Anyway, all that matters now is to win on Wednesday night.