It will not be too difficult for Dortmund to be able to enter the top 4, as it has happened since the past that this team is consistent enough to stay in the top board but they are not competing for the title.
Indeed Dortmund with their new coach will have a little difficulty but I don't think it's excessive.
Leverkusen and Bayern Munich will still be the favorites to win the title this season and I even think the competition this season will be much fiercer because Bayern Munich made many changes in the team.
And overall the competition in the Bundesliga has been quite fierce in the last few seasons we can see that the Bundesliga is getting more competitive.
Yes, most likely they will be able to, Stuttgart let go of many important players for the team and now I doubt that they will be able to stay at the top of the standings again. We will soon see what they are capable of in the match for the Super Cup with Bayer, by the way, bookmakers offer a odds 1.88 for Bayer to win, which looks pretty good.
And considering that Stuttgart will most likely be uncompetitive in the new season, Dortmund will have three main competitors left, Bayern, Bayer and Leipzig, so yes, they will be in the top 4. But that is not what is interesting, but what Bayern will be like.