They were even able to to win the German cup against Dortmund, winning yet another double.
So hats off and congrats to them.

Now let's take a look at the upcoming season.

Bayern won the league and the cup but losing that semifinale against Madrid the way they did left a bad taste in their mouths. Therefore Pep Guardiola will be allowed to add some more of his players.
Incoming:
Robert Lewandowski(Striker/Borussia Dortmund)
Sebastian Rode(Midfielder/Eintracht Frankfurt)
Outgoing:
Daniel van Buyten(Defender/?)
Lukas Raeder(Goalkeeper/?)

After losing that champios league final and Mario Götze to Bayern, they had quite some trouble with injuries and will now have to waive goodbye to Robert Lewandowski.
They'll try to compensate that with a deeper team and intend to keep Marco Reus for at least another season.
Incoming:
Adrian Ramos(Striker/Hertha BSC Berlin)
Ciro Immobile(Striker/Juventus)
Dong-Won Ji(Striker/back from loan to Augsburg)
Outgoing:
Robert Lewandowski(Striker/Bayern Munich)
Marvin Duksch(Striker/loan to Paderborn)
Manuel Friedrich(Defender/?)

Schalke started the season pretty badly and had some injury problems. Though, they managed to play through them and found out that their youngsters are usefull and able to play at the highest level.
Incoming:
Sidney Sam(Winger/Leverkusen)
Fabian Giefer(Goalkeeper/Düsseldorf)
Outgoing:
Timo Hildebrand(Goalkeeper/?)
Tim Hoogland(Defender/?)
Lars Unnerstall(Goalkeeper/Düsseldorf)
Anthony Annan(Midfielder/?)

After playing a very good first half of the season, Bayer nearly blew it away and needed the help of part time manager Sascha Lewandowski to at least finish fourth and have a chance to qualifiy for the champions league.
Incoming:
Wendell(Left Back/Porto Allegre)
Josip Drmic(Striker/Nuremburg)
Outgoing:
Sidney Sam(Winger/Schalke 04)
Jens Hegeler(Midfielder/Hertha BSC Berlin)

After winning the Bundesliga title a couple years ago, Wolfsburg was known to not spend those Volkswagen millions correctly and hardly made any noise. Though, since installing Klaus Allofs as manager and hiring Dieter Hecking as their coach, they've been able to form a very good team.
Now they'll certainly try to make a push for the champions league spots, hardly missing out this past season.
Incoming:
Aaron Hunt(Midfielder/Werder Bremen)
Sebastian Jung(Right Back/Eintracht Frankfurt)
Outgoing:
Jan Polak(Midfielder/Nuremberg)
Tolga Cigerci(Midfielder/Hertha BSC Berlin)

After having experienced international football for the first time since the 1990's, Gladbach missed out during the 12/13 season, finishing just short of those places.
After signing Raffael, Max Kruse and loaning Christoph Kramer, Gladbach played a brilliant first half of the season but couldn't keep it up. Though, they still managed a 6th place finish, now having a chance to qualify(EL Playoffs) for the Europa League for the second time in three years.
The upcoming season will be a tough test, given that Gladbach will need to replace Marc Andre ter Stegen, who finally joined Barcelona, and the best free kick taker in the world in Juan Arango.
Incoming:
Yann Sommer(Goalkeeper/FC Basel)
Fabian Johnson(RB, LB, LW, RW/Hoffenheim)
Andre Hahn(Winger/Augsburg)
Ibrahima Traoré(Winger/Stuttgart)
Outgoing:
Marc-André ter Stegen(Goalkeeper/FC Barcelona)
Juan Arango(LM/Club Tijuana of Mexico)
Lukas Rupp(Midfielder/SC Paderborn)
Elias Kachunga(Offensive Allrounder/SC Paderborn)

Mainz was able to pull of yet another great season, showing that they belong in the Bundesliga and are even able to make a run at the european spots.
This time they finished seventh and will start qualifying for the Europa League durint the 3rd round of qualifying.
Though, they'll have a tough task ahead of them given that they lost their coach(Thomas Tuchel), will most likely without Eric Maxim Choupo-Mouting and don't have a lot of money to built a squad able to sustain playing three competitions.
Incoming:
Nikita Rukavystya(Striker/FSV Frankfurt)
Chinedu Ede(Striker/Kaiserslautern)
Outgoing:
Zdenek Pospech(RB/?)
Bo Svensson(Defender/?)
Malik Fathi(LB/?)

After a two year hiatus in the 2nd Division, Cologne will be back in the Bundesliga and hopes to become a permanent Bundesliga site.
Incoming:
Mergim Mavraj(Defender/Greuther Fürth)
Pawel Olkowski(Right Back/Gornik Zabrze)
Dusan Svento(Left Back/Red Bull Salzburg)
Kevin Vogt(Midfielder/Augsburg)
Slawomir Peszko(LW/Parma)
Outgoing:
Adil Chihi(Winger/?)
Kevin McKenna(Defender/?)