I have heard a few different version of the intention behind ZFS license, through I can't say that for a legal case I have enough information to have a definitive opinion. Some people say that ZFS license was created with the explicit purpose to be incompatible with linux in order to not compete with solaris, but I would agree that Oracle has a thought case in court if they want to wait only to sue later. That is a practice that the legal systems tend to strongly dislike.
The other side is of course each one of the linux developers, each holding the full power of copyright. To cite SFLC, no free software developers have ever sued an other free software developer over license incompatibility, so its very unlikely to happen with ZFS. Such court cases really on happen between companies.
So to sum up, a case over ZFS is very unlikely, but I would not bet on what would happen if android suddenly started to use ZFS.
I think the Sun leadership at the time wanted ZFS to be on Linux up to the point of licensing it under the GPL. The employees wanted a more BSD-like license[1], so that's the correct context under which you can look at how Solaris was licenced. It's not about being in Linux or not, it's do we want Solaris to be under a more BSD like or GPL license. I think this conversation was bigger a decade or more ago, and frankly the GPL has had more commercial success since then. If Solaris had been GPL'd is an interesting thought experiment, and too bad it's just that. Netbeans was GPL and CDDL dual licensed.
I wonder what Linux Torvalds thinks about merging ZFS into Linux now, he wasn't too keen a decade ago. Sun is no longer around, someone worse like Oracle has taken their place. A couple of lessons for the open source community here, I think. And Brian Cantrill nails in on the head in the youtube video link.
ZFS will need to be on Linux first before it can show up on Android or media centers or gaming consoles, and I don't doubt Oracle's ability to find a way to patent troll anything. But it will be just that: patent or copyright trolling.
To add a couple more things: Oracle has been developing ZFS sans open source for the past few years as well, which means they've stopping caring about OpenZFS and/or have lost the right to.
Canonical, Debian and SFLC have really done with right thing by distributing ZFS on Linux, using AFS as a precedence. I hope more merging like this can happen in open source in the future.
The other side is of course each one of the linux developers, each holding the full power of copyright. To cite SFLC, no free software developers have ever sued an other free software developer over license incompatibility, so its very unlikely to happen with ZFS. Such court cases really on happen between companies.
So to sum up, a case over ZFS is very unlikely, but I would not bet on what would happen if android suddenly started to use ZFS.