I think that estimate sounds about right for the US, though you never know, they could match MX opening week figures.
Album sales have changed even from last year (down roughly 15% thanks to streaming) which is having an impact across the board. I think Coldplay does have a lot going for it though. They have always been a strong seller, there's been some good promotion (iTunes banner, Target ad), Chris being on The Voice, etc...and of course the break-up is a factor too. I think Ghost Stories could have a bigger opening than MX, but then fall down the charts faster. As the digital market gains each year second week drop offs are becoming bigger due to larger pre-orders.
Who knows...I could be completely surprised too :)
Luckily since the band is a good album seller relative to everyone else, the band has nothing to worry about.