If you are a class capable of dual wielding (eg: hunter, rogue, or warrior), you can wield two +skinning weapons (although Finkles is not off-handable IIRC), and the enchant on your gloves, maxing out at 325 skinning. At present, no mob exists with an internal level above 63 (although mobs such as this, ie: Magmadar, Nefarian, Onyxia, etc only display "Boss" for a level). Since no mob is set above level 63, you can skin anything currently in the game with 315 skill, but 325 means you will fail a bit less often.
In the expansion set, if you had 325, you'd be able to skin level 65 mobs at level 60, but I doubt you'd be killing many creatures +5 levels above yourself, unless at the new endgame there are mobs more than +3 levels above max level...