While I'm firmly in the 4:3 camp since that's how it was produced.
We all know people just want things to fill their screen, that's why most movies on cable are cropped to 16:9, and why Friends and Seinfeld when prepared for HD a few years back got 16:9 versions.
We don't know for sure that there aren't 16:9 versions being quietly made, or at least planned for. Back when TOS was remastered in 2006 they made 16:9 versions (live action cropped to 16:9 with new VFX rendered natively 16:9) for potential markets where widescreen TV penetration was higher at the time such as Japan. Apparently it did indeed air in Japan that way.
Its not about my personal preference, its whether content providers will want the shows in five to ten years when pretty much everything is in widescreen?
I'm aware of the cropped TOS episodes in Japan.