It will depend on the decisions you make in Mass Effect. Well, as far as we know, (or it already have been confirmed in another source)
Shepard (Will return) ---> Sources indicate that Shepard was "killed in action" But this information is yet to be confirmed. (But the Mass Effect community is sure that Shepard will return.) Ashley (Will Return) Wrex (Will Return) Garrus (Will Return) Tali (Will return) Liara (Will return) Kaidan (Will return) So, basicially, everyone will return. (Depends on your decisions.)
Look at the Mass Effect 2 information page which can be found http://masseffect.wikia.com/wiki/Mass_Effect_2 <--- There.