IMO most of the F/O's for the E-190 will be the same people who were Captains and F/O's on the E-170 for mainline. A large number of the current pilots flying the remaining E-170's are just planning to stay till the last plane leaves, collect furlough pay and unemployment, and then take the first avail recall late this year or yearly 07. Many will move into the right seat of an Airbus or 737, but many will come back into the Embraer.
The very same thing applies to the Flight Attendants currently flying the E-170.
And the people who know how to fix the E-170 are still here, and will be working on the E-190 as well as the remainder of the mainline fleet.