Here is forbes prediction with current dates:
Number Of Shows: 65
Average attendance per show: 55,000
Avg. Face Price: $88
Gross Sales: $314,600,000
I had some time on my hands and was looking up venues from Bey/Rih/Gaga's latest tours and comparing them to 1D's 2014 tour.
Forbes has already come out and said that 1D's tour this year could be one of the biggest of all time, and no Aus or Asian dates have been added yet.
(Wiki.... so probably not 100% accurate. I looked up the venues as well and most of it seems close.)
Some (mostly random) comparisons:
Netherlands dates:
Bey - Ziggo Arena: 17,000 seats - 30k Total Tickets Sold
Rih - Ziggo Arena: 17,000 seats - 33k Total Tickets Sold
Gaga - Ziggo Arena: 17,000 seats - 26k Total Tickets Sold
1D - Amsterdam Arena: 53,000 seats - Two shows scheduled with 70-100k possible
Milan dates:
Bey - Mediolanum Forum: 10k seats - 10k Total Tickets Sold
Rih - N/A
Gaga - Mediolanum Forum: 10k seats - 10k Total Tickets Sold
1D - San Siro: 80k Seats - Two shows scheduled with 110-160k possible.
London dates:
Bey - O2 Arena: 20,000 seats - 97k Total Tickets Sold
Rih - Twickenham Stadium: 82,000 seats - 95k Total Tickets Sold
Gaga - Twickenham Stadium: 82,000 seats - 101k Total Tickets Sold
1D - Wembley Stadium: 105,000 Seats - Three shows scheduled with 200-300k Possible
Atlanta:
Bey - N/A
Rih - Philips Arena: Seats 20k - 13k Total Tickets Sold
Gaga - N/A
1D - Georgia Dome: Seats 80k - One Show scheduled with 60-80k possible
Chicago:
Bey - United Center: Seats 23k - 14k Total Tickets Sold
Rih - United Center: Seats 23k - 16k Total Tickets Sold
Gaga - N/A (canceled)
1D - Soldier Field: Seats 63k - Two shows scheduled with 90-120k possible
LA Area:
Bey - Staples Center: Seats 20k - 28k Total Tickets Sold
Rih - Staples Center: Seats 20k - 14k Total Tickets Sold
Gaga - Staples Center: Seats 20k (Canceled)
1D - Rose Bowl: Seats 90k - Three shows scheduled with 150-210k possible
Sao Paulo - They are all using Estádio do Morumbi, but 1D have two shows..... while the others only had one each.
(Other than Amsterdam I really did just randomly click on dates.)