In addition to the points made by 'thesimon' about OneDrive pricing:
Apple's cloud storage offering includes 50GB ($12/year), and 200GB ($36/year) tiers. I'd bet 99% of Dropbox users could fit in one of those tiers and save a lot of money.
I have a 1TB OneDrive and 200GB iCloud, but I spend money on Dropbox because I trust them to be reliable. If the others catch up on reliability, where is the path for Dropbox's survival? (They're smart guys, so I'm sure they've thought about it)