Most risk comes from the management migration from R77.30 to R80.x, if that went well then you are up to go.
I've through many migrations of this kind and never come up with any IPS issues, if unsure you may set up a detect only profile and then switch to prevent in another maintenance window.
I strongly advice Tim's advice and unify the policy as soon as you are comfortable with the new version.
Please read on how the "Protected scope" column works on the Threat Prevention policies, if left untouched you will be applying IPS to both incoming and outgoing traffic.
Regards,
Federico Meiners
____________
https://www.linkedin.com/in/federicomeiners/