I heard that there would be atleast 120 challenges, 60+ on each side of the campaign, and, knowing criterion, and the fact that Craig Sullivan emphasized the word "DLC" on a couple interviews, there would probably be more.
Fortunately, longevity seems to not be a problem anymore, and if your into online it might even last as long or longer than paradise, which lasted a long time for me. :p
P.S: Minimum Specs for HP are very low, Almost lower than Paradise:
OS: Windows® XP SP 3 (32-64 bits) / Windows Vista® (32-64 bits) / Windows 7® (32-64 bits)
Processor: Intel Core® 2 Duo 1.8 GHZ or AMD Athlon X2 64 2.4GHZ
Memory: 1.5 GB Windows® XP / 2 GB Windows Vista® - Windows 7®
Graphics: 256 MB DirectX® 9.0 compliant card with Shader Model 3.0 or higher (see supported list)
DirectX®: DirectX 9.0
Hard Drive: 8.0 GB
Sound: DirectX 9.0 –compliant sound card
Supported Peripherals: Keyboard, optional controller
Recommended:
OS: Windows® XP SP 3 (32-64 bits) / Windows Vista® (32-64 bits) / Windows 7® (32-64 bits)
Processor: Intel Core® 2 Duo E6700 2.6 GHz or AMD Athlon 64 X2 6000+ or better
Memory: 1.5 GB Windows® XP / 2 GB Windows Vista® - Windows 7®
Graphics: GeForce 8800 GT or ATI Radeon HD 4700 or better
DirectX®: DirectX 9.0
Hard Drive: 8 GB free space
Sound: 5.1 sound card
Supported Peripherals: Keyboard, joystick optional (Xbox 360® Controller for Windows recommended)
1.8ghz dual core? 256 mb graphics card? Is it just me or is criterion really good at porting to the PC? They always make it run amazing, somehow...