You're right, those will be interesting battles, although they're basically going to occur in the party primaries. I think the only race which might be competitive in November is not the Martin Frost/Pete Sessions battle. It's the Charlie Stenholm/Neguebauerwhatizface matchup.
Even then, Stenholm will be the underdog.
#2 will have Democrat Lampson the B/PA local against the Republican out of the Houston area. I would think the Republican will win but it could make for some interesting side play....