Leaving a company after acquisition?

Hi, I’ve been the principal engineer for a small company for several years now. We are being acquired, and I’m a “key employee” but I’ve been undervalued for years and the “golden handcuffs” are nearly nonexistent.

I am strongly considering leaving upon acquisition, as I think my career will be quite limited by staying. My concern is that the acquiring party may feel “wronged” by my leaving so soon.

Is there some grace period that is considered “professional” in such circumstances? I’m not under a contract and there is little financial incentive to stay.

Thank you for any advice.