Yes. NIST SP 800-171 Rev.3 documentation can support future CMMC readiness.
A practical approach to implementing NIST SP 800-171 Rev 3 for CMMC future CMMC readiness is to maintain current CMMC Level 2 documentation for Rev.2 while adding Rev.3 mappings, DoW/DoD-provided Organization Defined Parameters (ODP) criteria, updated System Security Plan (SSP) language, revised standards and future-state Plan of Action & Milestones (POA&M) items.
ComplianceForge NIST 800-171 & CMMC Compliance Documentation: https://complianceforge.com/cybersecurity-templates/nist-800-171-compliance
NIST 800-171 R2 to R3 Transition Guide: https://complianceforge.com/start-here/nist-800-171-cmmc---where-do-i-start/nist-800-171-r3-transition-guide
NIST 800-171 R3 Kill Chain: https://content.complianceforge.com/pdf/kill-chain-overview-nist-800-171-r3.pdf
NIST SP 800-171 Rev. 3: https://csrc.nist.gov/pubs/sp/800/171/r3/final
NIST SP 800-171A Rev. 3: https://csrc.nist.gov/pubs/sp/800/171/a/r3/final
DoD CMMC Alignment to NIST Standards: https://dodcio.defense.gov/Portals/0/Documents/CMMC/CMMC-AlignmentNIST-Standards.pdf
