Does Google's true future in tablets rely on Android or Chrome OS? Both? Right now, it's easy to say Android. It's been around longer (Chrome OS isn't even in the market yet, beyond the pilot program).
A report from CNET says that Google has begun building a tablet version of Chrome OS, citing source code. Google said in a statement, "We are engaging in early open-source work for the tablet form factor, but we have nothing new to announce at this time."
Google has said in the past that Chrome OS and Android will likely converge one day. Specifically, in late 2009, co-founder Sergey Brin is quoted as saying, "Android and Chrome will likely converge over time." There's no telling when or if this will actually happen. If it does, it's not likely anytime soon.
Clearly Android is doing well. It's market share is expected to reach 50% by next year. Meanwhile, Google is clearly putting a fair amount of energy into Chrome OS. Again, it's not even out for the general public yet.
If the two are to converge in time, Google will wait to see how each product evolves, and combine the best features of both. Android will have a solid lead, but the Chrome browser is gaining in popularity too. It will be interesting to see how the public interacts with it.
In some ways it makes a great deal of sense to make a tablet version of Chrome OS, because tablets are becoming much more "in" than laptops/netbooks, and if they want a lot of people to use the operating system it will help to be on more devices.
Google expects Chrome OS to be a major force in the enterprise, and to help push Google Apps, don't forget - a key area where it competes with its main competitor, Microsoft.