I stilll drive my 1988 Yamaha FZR250 daily, it's such a nice little bike and when I tried the Ninja 250 a few years ago I couldn't believe this piece of crap (compared to my bike) was still being sold over 20 years after my bike was released.
But the Ninja 300 was a nice upgrade and that R3 seems even better and cheaper. It's also really close to my FZR on paper, except for the missing cylinders (42 vs 44hp, 368 vs 350lb or so).
The R3 will miss the high revs pleasure of my I4 (over 17 000rpm) but the more modern suspension and stronger low/mid end torque should more than compensate for daily driving.
Otherwise, I don't think this rumor is true. Before doing a crazy high tech 250cc, I think that kawasaki would start by launching a nice mid size 3 or 4 cylinder bike. Except for the supersport ZX6R, their smallest 4 cylinder bike in North America is the Z1000, which is too expensive and too powerfull for many.
This is very true, from how i see it they're good enough with just one 250, doesn't make sense to have 2, i'll be surprised if that's something that actually happens.
Yamaha and Honda both have a few bikes in the 6-700cc range with different engine layouts and performances. There is room for two models with the same engine size, but an I4 250cc would be a bit stupid since 250cc isn't a "magic number" anymore in most countries (for insurance groups or driver licenses). If someone launch a 4 or 500cc I4, then I would be really happy since I find the 600CC+ I4 too powerfull for my needs and they cost a lot in insurances.
So how does an I4 feel and drive different from a V-twin? What are the benefits and disadvantages?
The I4 has more top end power and is incredibly smoother than a V-twin.
The V-twin has more low end torque and unpleasant vibrations (what people call character sometimes).
But the R3/Ninja300 have parallel twins, not V-twins. They are in between, with a bit more vibrations and torque than a I4 but not that much, and lower revs.