You threw us off a bit when you mentioned you had a 4/3 camera. 4/3 sensors are not in the P&S realm. Camera's with 4/3 sensors (actually micro 4/3 mirrorless) already have interchangeable lenses. Olympus and Panasonic are the only mfrs using the original 4/3 and micro 4/3 sensor.
The sensor in your camera is similarly sized to the 4/3 sensor.
Interestingly, the camera you do have was upgraded to a sensor that is just slightly larger than a 4/3 sensor, but otherwise the camera is the previous G series Canon, and is fixed lens, which you clarified by telling us the actual camera halfway through this thread.
You cleared the air on that when you indicated you have a fixed lens with a 1.5 sensor.
With that in mind, some of the posts made to your question have been off the mark a bit.
Wondering at this point if you are still confused by the potentially erroneous information.
So, to clarify.... there are "bridge" camera's out there that can very likely give you superb image quality with what you have, particularly for the market you are using your camera in. Your camera falls more easily into a Bridge Camera category, but with a bit larger sensor than most bridge models. The sensor is the camera's strong suit. I am going to link the conclusion page on your camera's review at DPreview, a well known an popular camera review site, at the end of this post.
Yes, larger sensors and interchangeable lenses add flexibility to the process, but they also add complexity to the craft of photography. The question is, how much time and money do you want to invest to become a more proficient photographer, or do you want to simply take good enough images to increase your income from selling/brokering Real Estate.
The first is photography and the second is "marketing" Real Estate.
It's quite likely that if you learn more about the craft of photography, and as much as possible about the camera you now own, you will be able to enhance your images to be as good as what you see from others in your business.
I was confused at first on your post, and only began to understand your confusion upon finally finding out what camera you do own. Not a 4/3. A 4/3 sensor camera... Olympus or Panasonic with the ability to change lenses would be an excellent option for you.
However, the camera you now have may do you just as well purely for the reason you seem to want to upgrade your skills. Not necessarily your equipment.
The review at DPreview:
http://www.dpreview.com/reviews/canong1xI generally go to the Conclusion page for the summary by DPreview, but this is their whole review.