So it sounds like as you've rooted, your carrier won't be supplying any updates as it recognises the fact you've rooted. No problem. You can still update to the latest firmware, and probably quicker than your carrier would provide!
You will need to flash a custom rom, which there are loads to choose from and available from the xda forums (I cannot provide a link at the moment, I'm on my phone). There are different types of roms, plenty of which are Samsung based so you can keep the touchwiz/stock feel. Alternatively there are other roms which are just Android as google intended (like the Nexus) and various other types. I guess it's all down to you to find what works for you!
Good luck!