Tuchel had emerged as one of the favourites to take the reins in 2018-19 after Heynckes - who replaced Carlo Ancelotti in October - made it clear he would not continue beyond this season.
The German led Bayern to a sixth consecutive league title but that was not going to stop him from calling his managerial career to an end again, with Bayern finally announcing his replacement.
Kovac's current assistant coach, and brother Robert Kovac will join Bayern as well.
Here are three winners and three losers.
Bobic blasted Bayern on Friday for the timing of its announcement that Frankfurt coach Kovac would be switching to Bayern next season, and for not getting in touch beforehand. "I hope that's a good omen". "I have good memories of our treble season".
He has seven goals in his last nine Bundesliga games for Bayern Munich, but Germany global Sandro Wagner knows there is only one king in Munich, and the rest of the world, for that matter. "That's how it happened", Kovac said.
"Frankfurt now has months to look for a successor (for Kovac)". Liverpool's triumph in '84 was its fourth in eight seasons but it had been a decade since the Merseyside club reached this stage of the competition.
Bayern had appointed Kovac as he is familiar with the Bavarian side, having played for them before.
"We are therefore convinced that he is the right coach for the future", Bayern's sporting director Hasan Salimhamidzic said via the club's official homepage.
"He told us that he had already decided. One has to accept that, but it's not a problem for us".
"He's a young coach and he has done well at Eintracht Frankfurt", enthused the Colombian, who top-scored at the 2014 World Cup with six goals.
Injured when Croatia finished third at the 1998 FIFA World Cup in France, the Berlin-born 46-year-old went to win the double of Bundesliga and DFB Cup with Bayern in 2003, and James has little doubt about the coach's ability to swell both of their trophy cabinets.
His first full season in charge brought an 11th-placed finish but Frankfurt did reach the final of the DFB-Pokal, where they narrowly lost 2-1 to Borussia Dortmund.
The holders have been drawn against the newly crowned Bundesliga champions in a repeat of the last-four tie from five years ago, which Bayern won on penalties.
However, the Suddeutsche newspaper claimed that Bayern met Kovac two weeks ago to discuss the job.
But now the dream of managing Bayern is over, for the time being at least. With Real looking vulnerable despite Ronaldo's extraordinary performances, Bayern has a chance to provide their coach with the ideal send-off - and even provide a little bit more romance.