I hardly see a reason for panic. Apple having the trademark for the word "Apple" doesn't stop any apple seller from slapping the word "Apple" on every box of apples. As long as a word is used for descriptive purposes it is not violating trademarks.
No startup will ever use the word "startup" in its trademark.
Unless you’re a company catering to startups, the association is a temporary one. You either become a grown up company (in which having ‘startup’ in your name is silly), you get bought out (in which the name disappears), or you go bust. There is no such thing as a permanent startup.
No startup will ever use the word "startup" in its trademark.