Brands move hither and yon all the time.
Sometimes you read/hear about it. Sometimes you don't.
Sometimes you notice changes (good or bad) in the products. Sometimes you don't.
I think it's too early to tell whether the Sennheiser line of headphones will change, or how such change might play out.
But consider: Your mother believed that GE stood for General Electric. And she was right.
She owned a GE stove, refrigerator, washer, dryer, clothes iron, and light bulbs.
But that was decades ago. Today those products (most of them) are still made under the GE brand, but NONE are made by General Electric. Nor are they sold by General Electric.
The GE refrigerator brand is licensed (owned?) by Haier in China. Big surprise, right?
We own a GE chest freezer. No problems in 7 years, so that's a good sign. Maybe the brand will live on?
It is/was a similar story for RCA products. The brand went to GE (when GE still meant General Electric).
It was then licensed to East Asian manufacturers. So there was no RCA nor GE content. Just the RCA label.
Eventually that brand lost its cachet, and I think it was dropped a decade or more ago.
Likewise for a host of other American brands.
Anyway ... who knows what will become of Sennheiser phones? I might find out when my three-year-old phones need replacement.