The past is not always a predictable measure for the future, especially as you don't know Oracle's agenda.
They might just wait until there is more money to be gained from a lawsuit or until there's more people already on ZFS who don't want to have anything less.
the courts will not allow that. you may claim that you recently discovered that there is infringement or you can claim that you are a new owner of a patent and are enforcing it.
But I dont think courts will take too kindly to someone who knowingly sat without doing something and waited for it to become big.
I would assume that Canonical has already sent infromation about this to Oracle. If they havent done anything now, they cant do anything later.
We at Canonical have conducted a legal review, including discussion with the industry’s leading software freedom legal counsel, of the licenses that apply to the Linux kernel and to ZFS.
And in doing so, we have concluded that we are acting within the rights granted and in compliance with their terms of both of those licenses
They might just wait until there is more money to be gained from a lawsuit or until there's more people already on ZFS who don't want to have anything less.