I am just going to say that a 30-50hp electric tractor sounds amazing for me. I assume it will be much quieter than my tractor and my ears aren't getting any better. I would love to be able to have a conversation without turning the tractor off. Charge time and run time sounds great, but I have a hard time getting more than 4-5 hours of work in at a time anyway. Nearly 100% of our local energy is hydro, so its pretty clean.
As far as the future goes, I think that eventually there will be non-diesel tractors that are better than our current ones (all of them). I just don't think we are there quite yet. However, having options isn't a bad thing.
For emissions then I have know that this particular replacement might not turn the tide of greenhouse gas emissions, but every little bit helps. I would imagine that for maybe everyone but someone on 100% coal, the energy used to produce the charge is probably a little cleaner overall than burning the diesel fuel.
For the big picture, something like 54% of greenhouses gasses come from transportation and electricity generation, so those should be our targets first. Personally I think that modern nuclear could be a big help, but I also know that every wind and solar plant gets us closer. Electric cars and trucks can help, as can requiring those generators who can't change (air and sea travel) to contribute to reducing emissions in other sectors. I would love for my kids to be able to enjoy the environment as much as I have. We shouldn't let perfect be the enemy of good.