From price point of view, this lens sits between the 400 2.8 ii and 600 4.0 ii. it combines the shorter FL with the slower aperture.
At the wide end, a 200 4.0 isnt really spectacular, its available for about $1200, means for this amount a 400 2.8 and a 70-200is is available. if a speed of 4.0 is enough, a 500 4.0 looks like a bargin and with a 1.4 ext and a 2nd body its as flexible and gives more reach.
so the new lens would be fine but for this price its really specialised, and only an answer if 200-300mm cant be done with a 2nd, way cheaper lens. If it would be priced between the 300 2.8 and 500 4.0 it would be more interesting. as far as i know, the Nikon is prised in this range, but not sure about this.
to price it logically, the price must be reduced by 25% or the priced of the other teles must be increased the same amount, so its our guess what canon might do if the new lens wïll be no success