Do I still get severance if I decide I don't want to work for the new owner?

It depends on why your employment is actually ending, not simply on your personal preference not to work for the new owner. If the new owner offers you materially the same job on materially the same terms and you simply choose not to continue, that's generally treated as your own decision to leave rather than a termination, and typically doesn't trigger severance or notice obligations, since you weren't let go — you resigned.

If, on the other hand, the new owner isn't continuing your employment at all, or is offering you a position with meaningfully worse terms — significantly lower pay, a demotion, relocation, or similar — and you decline those worse terms, that can be treated very differently: as a termination, or a constructive dismissal, rather than a voluntary resignation, which can bring you within your usual entitlements to notice or severance.

The line between "I just don't want to" and "the new terms are genuinely unacceptable" is exactly where these situations get contested, and it turns on specifics — what changed, by how much, and how it compares to your old job. Get the actual new terms in writing first and have them assessed before deciding how to respond.