Source: Hasbro Catalog Page
Link above has 2011 Nerf information as well.
Looks like the Super Soaker Hydro Cannon will be ~76cm long or so.. that's basically the same length as the Monster (2001)/CPS4100, though definitely looks less bulky than the older blasters.
Super Soaker Point Break is ~26cm which is about the length of a Super Soaker XP20 /Max-D 2000.
Super Soaker Scatter Blast is ~41cm which is about the length of a Super Soaker Arctic Shock, Vaporizer or Defender.
Super Soaker Thunder Storm is ~35cm which is about the length of a Super Soaker Triple Shot.
Super Soaker Tornado Strike is ~52cm which is about the length of a Super Soaker XP-90 or just slightly shorter than the Super Soaker XP310.
Granted, all lengths are based on package size so the actual blasters may be slightly shorter.
Edit: links appear and disappear oddly... here's a direct link to the Super Soaker PDF file




