I don't think it's going to be that radical a change tbh. MP-05 was always a crap figure - even ignoring the scale. The fact is that with only a week's timeframe in terms of its development as I understand it, it's a miracle the figure is as good as it is, MP-36 was always necessary, even without the scale, because the old MP figure had never been given its proper due.
Then there's Prime. The fact is that people forget that the Masterpiece line as we know it is actually two separate toylines. Everything from MP-01 upto MP-07 was actually part of the same meta-toyline as Binartech, and we did get a crapload of Autobot Cars for that toyline. When the decision was made to go cartoon accurate and downsize compared to the 1/24 scale figures, Optimus Prime getting a 2.0 was always a given.
However is MP-10 a better engineered figure than MP-01?
Owning both figures, I have to say that the answer is no. Also where MP-01 has more animation accurate proportions, MP-10 is alot more squat and stocky in comparison.
If I were Takara, I'd almost be tempted to downsize MP-04, modify the design slightly where parts need reinforcing, and then pass it off as MP Optimus 3.0. Once that happened, I'm not sure you could improve on the figure enough to even remotely justify a 4.0, just as I doubt we'll ever see a Megatron 3.0.
Except arguably Optimus 1.0. I have to say that as great as MP-10 has been in terms of scale, it really wasn't up to the same level of engineering as MP-01 imho.