Makes sense to pair Montreal with Miami travel wise but weather could be an issue in Montreal that time of year. Not sure how happy Monaco is to have their race moved off of their holiday weekend although I doubt that will have much of an effect on ticket sales.
What does concern me is the plan to start alternating tracks on a regular basis, there is talk about Spa being every second year alternating with the Dutch GP. I understand the idea as there are a ton of other venues that want a race but Spa, Silverstone, Monza, Monaco and Suzuka are 5 that I would hate to see go to every second year. IMHO Spa, Monza and Silverstone should as close to untouchable as it gets.