CDU - the Christian Democratic Union of Germany is the major party of the center-right in German politics:

The CDU has headed the federal government since 2005 under Angela Merkel, who also served as the party's leader from 2000 until 2018. The CDU previously led the federal government from 1949 to 1969 and 1982 to 1998. Germany's three longest-serving post-war Chancellors have all come from the CDU; Helmut Kohl (1982–1998), Angela Merkel (2005–present), and Konrad Adenauer (1949–1963). The party also leads the governments of six of Germany's sixteen states.

--CDU, wikipedia

CDU currently forms a coalition government with CSU (Christian Social Union), and SPD (Social Democratic Party). CDU and CSU hold an agreement that CDU does not run candidates in Bavaria, while CSU does not run candidates anywhere besides Bavaria. In forming this alliance, it is not unlikely that CSU may appoint the next chancellor following the elections, even if they win fewer seats than CDU.

The 2021 German federal election is expected to be held on 2021-09-26, the date chosen by President Steinmeier. However, there is still a possibility of the snap election at an earlier date.

As of the moment of writing this question, the CDU/CSU union steadily leads in election polls. In Vox's Future Perfect series, Dylan Matthews forecasted an 80% chance that CDU will continue to govern Germany throughout 2021.

Will the Chancellor of Germany following the next election be from the CDU/CSU union?

This question resolves positive if the Chancellor of Germany is from the CDU or CSU when they are elected after the next Bundestag Election. If they are a member of any other party, the question resolves negative.

The election need not happen on 2021-09-26 nor must the chancellor be elected immediately. In the case there is an acting government while parties negotiate to form a formal government, this question will wait to resolve until a new government is formed.

In the case an election is scheduled earlier, the question will close 1 day before polls are opened.