I thought the Sport was being discontinued. That was the word from Oshkosh last summer. Perhaps Katie can clear up what the status and future status is.
As any electronics company should, we have eventual plans for replacing the Sport, but that is way down the road. The Sport has been gaining popularity lately, now that people are learning how much it can do compared to the other EFIS systems out there in its price range. When we do replace it, we'll keep supporting it. There are dozens of our original Horizon I "WS" screens still flying. We discontinued those several years ago, but we still service them and release software updates for them when necessary.
The Sport started out as a basic VFR system, and that's how it is currently marketed-- for airplanes like the RV-3, RV-4, Panther, LSA, etc. Due to the requests of users over the years (JAMES!), we've added a lot of capability to it, so you can customize it to what you want. This is great for someone who buys an airplane with a basic Sport and they want it to do more stuff, or if they start off VFR on a tight budget, but decide later on they want to add capability and get their IFR ticket.
With a Sport system and its internal AHRS, you can only have dual AHRS if you have dual display screens. The HX(r) system is designed for flexible IFR redundancy--it can give you dual AHRS whether you have one screen or 2 or 3. In a multi-screen system, each AHRS can physically feed attitude information directly to any screen (up to 3) in case of a failure somewhere in the system.
As for serial ports and ADS-B- The older Sport HS and WS units do not have the right type of USB hardware for ADS-B data, so they require a serial connection for ADS-B. However, the Sport SX is capable of receiving ADS-B information through the USB port from the iLevil AW or SW, Radenna SkyRadar and Dual XGPS170. You'd need to install a powered USB hub, but that also expands your USB port count and enable charging for phones, iPod, etc. So, serial connection for ADS-B is not as much of a concern with newer Sport units.