There will probably always be a market for both. Carbs are simpler to work on and if you are in an environment that requires simplicity then maybe it's the way to go. Plus there is a price break. Some folks just like older technology because that is what they are familiar with. The carb on my 400 gets cranky sometimes but still works great. The one on my 425 works well too, but requires a lot of choke on start up, no matter the season.
For those with fuel injection, I gather it's electronic and there is a PCM/ECU squirrled away some where on the tractor? If so, with as much vibration and heat is on a garden tractor, I am surprised there are not more failures of fuel injection units due to computer issues. It would seem JD has it worked out.
With all the entry level tractors out there and their inflated (in my mind) prices they charge, I doubt you will ever see carbs completely wiped out. The technology is too cheap and reliable not to use to increase profits. Adding fuel injection to a D100 would either kill the profit or jack up the price as to make it unaffordable.
Another example of this as I wonder off topic a bit, is I did a top end rebuild on my buddies 99 Honda Civic a couple of years ago. It was the first Honda I had worked on and I expected a bit of cutting edge technology because Civics get such good mileage. Not so. While it had fuel injection, it still had a distributor. Most cars of that class had switched to distributorless ignitions back in the early to mid-90's. So the point is, there will always be a use for older technologies as corporations leverage them to max profits etc. Besides if it works, why change just to change?
The only thing that will kill off the carb will be emissions regulations. That's what did them in on cars. A carb will deliver similar fuel usage rates if property tuned, but that's a manual process. With electronic fuel injetion that is an instant and constant process handled by the computer.
