Virtualization Manager Primary License Limit

You'll get a problem polling the vsphere that puts you over, you can shuffle them a bit if you've got loads of vspheres.
Trying to remember exactly what stops, but it's more toward the "it stops" end rather than the "it's inconvenient" end.

It has been awhile since I looked at the specific logic but as Adam said, some stuff will stop monitoring. I believe it is generally a FILO situation or, said another way, stuff that has been "in" for awhile will stay "in" but there are some situations where that might not work perfectly so it is best to use the permissions on the VMware side to remove permissions from the polling credentials for less critical things so that your more critical items stay monitored consistently until you can bump up your license. If you are relatively certain your management will green light a purchase of a larger license, you can reach out to your sales rep and they might be able to provide a temp key for the higher socket count while the purchase is put through so you don't have to play whack-a-mole.