Matheson will be able to find at least one district where he can win. He was heavily redistricted in 2002 and still survived in a ~70% Bush district.
UT has often had a strange habit of electing 'Rat Congressmembers even in heavily GOP districts. Although Matheson barely won reelection in '02, there were some that said he didn't draw the strongest possible opponent that year, nor in '04 or '06. Presumably he'll remain until either Hatch or Bennett retires to try to take a run for the Senate. A 'Rat hasn't won a Senate race there since 1970. Personally, I oppose this 4th seat move solely because this is an attempt to give DC a full-blown voting House member, which strikes me as Constitutionally dubious. If we're going to empower DC, why not give the Conservative GOP Resident Commissioner from Puerto Rico a vote, too ?