Not all of the features are coming to the S3, as some of them rely on new sensors and other possible new additions to the phones chipset. I would say most of the features that are software based will see it, yes.
As for the look of the phone, Samsung knows what it is doing. They introduced the S3 with a different look from the S2. The S4 is as close to the S3 as they want it to be, but with a slightly larger screen. They are building their line with brand recognition. Apple does this by not changing the iphone drastically for years on end.
They want people to see the design and know if it is a Samsung Galaxy device. This is the reason why the Note phones and tablet as well as the tab line of tablets are all starting to look alike. It is a growing ecosystem. No one will be able to say "Is that an iphone or a galaxy S4?".
As for the colors, people complained about having black phones for so long, now that they come in colors, people are like "oh my gosh, where is my black phone that we used to have". I just wish they would bring the red versions out first sometimes or at least make them available at launch instead of waiting for christmas or valentine's day.
The screen is another gripe a lot of people have complained about. Frankly, a pentile screen at 441 ppi seems like a reasonably good screen. I am not going to break out my microscope to count jaggies on the screen instead of enjoying what is in front of me. Take HTC's washed out LCD screen that strains to show deeper black color or brighter colors. And also, as screens get bigger, the amoint of ppi does matter, even for pentile screens as it helps to make the resolution denser to the naked eye. Technically, to coin a Apple word, retina.
Will this screen see the Note 3, probably not. Unless Wacom can make their digitizers qork on 1080p screens. They work best in the 720p range.
But people are still going to hate because there is no Apple on the back, or HTC logo, or Moto insignia, etc.
Galaxy S4 or Note 3 for my next. Decisions, decisions.