If you can't find a projector with RS232... you're not looking too hard... Most projectors I've seen installed in presentation rooms are controlled over RS232. Also, the projector running above my head right now is RS232.
No, RS232 support should not be "dropped" - that would be very dumb... why would we take a step backwards? we're trying to support MORE hardware not less... Lots of people are using RS232 successfully - including me. Lots of devices manufactured today can be controlled by RS232... just because the projector you want isn't, doesn't mean that the receivers, televisions, cable boxes, and other special devices that other people have don't use it... you need to look at the bigger picture before you suggest dropping a feature that isn't useful to you.
Also, TCP/IP over Ethernet (the stuff that probably comes out of this RJ45 jack you're talking about) is supported... so is USB...
http://wiki.linuxmce.org/index.php/Control_A/V_equipment_with_RS232/USB/Ethernet