Things will likely still work, but understand beyond the QA-tested limits, YMMV. If you run into issues and need TAC Support, prepare to be told to scale back your policy count.
For the scale count it depends on a couple things. There's the system-supported (software version) limits, then there's the HW limits. various leaf models may have lower scale limits, so best to confirm with the supported scale of your platform. You can do this by looking under Operations > Capacity Dashboard.
Another way to modify scale is to adjust the Leaf Tile Profile - this allows you to tweak the Learning tables based on the function and endpoint type (v4 vs. v6). There's also profiles that tweak for IPv6 deployments. None of the Leaf Profiles will adjust the number of EPGs or BDs, but it will affect other learning tables.
Robert