As things look top 4 will be a push for them, but still very early days.
My prediction is that they will do worse then last season despite the fact they have most expensive squad ever assembled, a manager appointed for short term success and the highest wage bill. Somehow this will not be billed as a failure by the media but instead by blamed on LVG and with United being the great club they are doing it the United way and giving the manager time.
Then next season they will spend A LOT again (addidas deal is irrelevant they are still wedged) and see if they get lucky, I see them going all out for Bale/ Griezman etc. But being they are actually worthy of huge fees as opposed to Pogba (who don't get me wrong I would have been happy if we brought, but the fee which was £89 million, plus about £20 million to the agent (always forgotten) was far too much and no one else would go near) there will be competition this time from other attractive options. So they will get the next tier down the big names, but with something not quite going for them at that moment, a Rodriguez or someone like that if not working out for them at their present club as well as taking successful players from the so called lesser Premier League teams who have done well the previous season. Then all the reports will be about Mourinho's excellent record in the second season, how United are ready to challenge for the title with their team of all stars.
All the time us, Spurs and Liverpool will be improving with a long term plan and targeted recruitment, with players suited to the style of play and in the areas of weakness. United will end up being even further behind us (especially if Rooney is still there) and end up battling with Arsenal, Chelsea for 4th (although I wouldn't be surprised to see either of these clubs having moved ahead of United and closer to us, Spurs and Liverpool).
I could of course be wrong, but that is how I see it going based on what we can see at the moment.