He has a release clause this summer.
This idea that Bayern pillages their rivals in the Bundesliga is really not correct. Bayern and Dortmund rarely do business. Hummels is the only good player since 2014 that has been exchanged between the clubs. I believe his initial move to Bayern and subsequent move back to Dortmund were both heavily influenced by personal family reasons.
Leipzig also doesn't do much business with Bayern, and given how they've started to compete with Bayern recently sporting-wise, I don't see them doing much business with Bayern either. There's not much they can do at this point with Upamecano. The guy has a release clause. Someone was always going to activate it. Bayern's done so.