Is there any roadmap to be ESI partners with Microsoft?

ESI is generally not an open partner program that companies can simply apply to join. Access is typically provided through Microsoft/customer agreements and eligibility criteria.

If you're trying to get your organization onboarded, the practical route is:

Check with your Microsoft account team / Microsoft Customer Success Account Manager (CSAM) about ESI eligibility.

If you're a Microsoft partner, ask your Partner/Account Manager whether your organization qualifies through an existing Microsoft agreement.

Confirm whether your organization has an eligible Enterprise Agreement or Microsoft customer relationship.

Once eligibility is confirmed, Microsoft can provide the appropriate ESI enrollment/onboarding process.

So there isn't really a public ESI partner roadmap the first step is confirming eligibility with your Microsoft account/partner contact.