It will be called Piedmont. Part of the reason it is occuring is because Allegheny's leases on its Dash-8's are starting to run out. Allegheny is not renewing those leasings. Also, Allegheny pilots voted down the original RJ plan for Allegheny because it meant giving half of those positions to furloughed mainline pilots, thus hurting some Allegheny pilots.
So Allegheny was not getting any RJ's, and losing its Dash-8's. There has been increasing maintenance done on its Dash-8's as a maintenance base in BGM was shut down, and now crew bases are being shut down in BGM and SCE. Due to fewer and fewer airplanes being available, it was impossible for Allegheny to survive as a company. The merger of Piedmont, who will have more Dash-8's, allows all Allegheny and Piedmont employees to merge into one, in order of hire date.
US Airways also has said that this will be more practical than having two wholly owned turboprop carriers. Instead, there will now be one wholly-owned express turboprop carrier (Piedmont) and one wholly-owned express RJ carrier (PSA).