Jerry posted a great article about this to the blog: Why Samsung switching smartwatches from Android to Tizen maybe isn't that big a deal. Here's one section:
So far it looks like the interface has been ported over to Tizen, but left otherwise unchanged. Assuming that's the case, the experience for the end user will likely be very similar to that of the first-generation Gear.
So why did Samsung do it?
This is an easy one. Samsung spent a lot of money contributing to the development of a new open-source operating system for their consumer electronics division. Some folks love Samsung, others think Samsung is evil, but in the end Samsung is a business and they want to get a return from their investment. Since you don't need Android on your smartwatch to communicte with your Android phone (see Pebble), and Tizen is so scalable, the Gear 2 and Gear 2 Neo were a perfect place to use it. Samsung gets a return on their time and money spent developing Tizen, and has a stable and mature platform to build Gear-specific apps and functions on top of.
Because Samsung is part of the team that develops Tizen, it can also iterate and add new features on its own time, not Google's. Because the Gear UI (I'm going to call it GearWiz) is a simple event-driven layer on top of the OS, features can be added almost at will to the operating system with minimal change in what the user sees. We're creatures of habit. We like version two to look and act like version one ? hello iPhone.
This doesn't mean that Samsung is abandoning Android on their smartphones. That's just silly, and people need to stop saying it. Android puts billions of dollars in Samsung's bank account, and they don't have to spend money developing it from the ground up. When that changes, then we can discuss Samsung abandoning Android. In the meantime, be ready for a new Galaxy S device, and a new Note in 2014, and they will run Android. Same with 2015, I'll bet. Android is easy money for Samsung, and every company likes easy money.
So far it looks like the interface has been ported over to Tizen, but left otherwise unchanged. Assuming that's the case, the experience for the end user will likely be very similar to that of the first-generation Gear.