Ask HN: Grandfather in old SaaS prices or not?

Throwaway here.

I run a small saas service (~600 active paid users), and am planning on increasing prices next year. I think I have pricing laid out now, but the last remaining factor is whether or not to wholesale increase the prices for everyone already on the platform, or just new customers and upgrades.

Product is developer focused, and prices increase is just under 2x.