The only solution I could think of from a security standpoint would be to limit functionality on the device itself to such a level that there is not much need for updating, i.e., ideally the fridge becomes a dumb device that essentially offers a vnc-style connection to a central FridgeCo data center, so that the fridge itself would never deal with your passwords etc. other than sending them somewhere in an encrypted connection. This basic layer of functionality (and even that would be a lot to keep secure) would be more reasonable to maintain and keep secure than having separate apps for Google Cal etc. Of course, this would cause many more problems, be a single point of failure etc., but I think that's the way it's most likely going to go.
How much vendors are willing to use something like this remains to be seen. Personally I resist buying things that I think will have a poor security update record. I'd like to see more pressure on vendors to do the right thing here, especially because there is at least one reasonable solution available.
Disclosure: I work for Canonical, but am not associated with the IoT work in Ubuntu.
I believe Canonical have a grand plan but have just focused on phones first. Since to my knowledge the Ubuntu TV hasn't happened yet, how can it be a flop?
We have a dozen known vulnerabilities in common software packages every year, and these devices are using IP for communicating often confidential information. It can be disastrous for your toaster to be hijacked, especially if it can be remoted no and burn your house down.
This whole IoT disaster should have been predicated on free software, with some protocol support for authorized local network updates and maintenance. You know damn well that if Samsung cannot be bothered to update the OS on a four year old phone anymore, your Samsung Fridge or TV or futon is a lost cause.