You may not have seen Klance get explicit confirmation onscreen, but there is much evidence to the contrary that you have every right to believe that they would have been endgame had the series continued. Here are all the major moments that confirm Klance is canon king (no matter what anyone has to say about it).

Was Klance supposed to happen?

so basically klance was originally supposed to be endgame and then they changed gears after s3, but some of the artists and writers continued to create romantic coded klance scenes because they KNEW that was supposed to be where it was going originally.

Who does Keith end up with?

Some fans expected Keith and Allura to eventually end up together because they did in previous versions of the story. In fact, he married her and became the King of her people in the animated series.