2/3rds of this team is weak to Ice, and that's not a good thing. Even though Mamoswine dropped to UU, it can wreak havoc on the team if it gets a free switch. Keldeo as the lone Ice resist won't be enough. As weird as it sounds, use Bronzong over Celebi. It resists Ice and still sets up Stealth Rock. You could use Heatran too, but be aware of the Ground weakness:
Bronzong:
-Stealth Rock
-Gyro Ball
-Earthquake
-Toxic/Hidden Power (Ice)/Protect
Nature: Sassy
EVs: 252 HP/4 Def/252 SDef
Item: Leftovers
Ability: Levitate
Heatran:
-Magma Storm/Fire Blast
-Flash Cannon/Hidden Power (Ice)/Stone Edge
-Earth Power
-Stealth Rock
Nature: Timid
EVs: 4 Def/252 SAtk/252 Spe
Item: Air Balloon
This team absolutely needs Rapid Spin/Defog support simply because Talonflame is 4x weak to Stealth Rock. Altaria is also weak to Stealth Rock before it Mega Evolves. Starmie would be the best fit in this case, IMO, even though it overlaps with Keldeo:
-Hydro Pump
-Psyshock/Thunderbolt
-Ice Beam/Hidden Power (Fire)
-Rapid Spin
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb
Ability: Natural Cure/Analytic
or
-Scald
-Psyshock/Reflect Type
-Rapid Spin
-Recover
Nature: Timid
EVs: 248 HP/32 Def/4 SAtk/224 Spe
Item: Leftovers
Ability: Natural Cure