Um, I'd go with Knowledge Planes as your 2nd Knowledge skill. Outsiders tend to have a lot of wonky resistances, immunities, and special abilities, so learning about them is pretty important. Local is kinda buggy, since you only learn about the base creature type. For example, if you encountered a level 20 orc wizard and a level 20 orc fighter and you rolled Knowledge Local on both, you would get the same info. Orcs are strong, have darkvision and light sensativity, etc. There just isn't a lot to know about them. Whereas if you did a Knowledge Planes check on a Nalfeshnee, you might learn that it has a Stench ability, Lightning Immunity, Blasphemy as a spell-like, and the ability to gate in more demons. Thats much more useful than learning that orcs have darkvision. Knowledge Local has a lot of other RP aspects (such as finding out if the duke has a daughter, or learning about the debts a certain merchant family may have) but that can also be obtained by a Lore check, so it may not be a huge issue if you don't have many ranks in it. Another good idea, especially when you get your loremaster levels, would be to drop 1 rank in ALL knowledge skills. Knowledge skills are trained only, so you can only roll if you have at least 1 rank. Who knows, you may roll high.
UMD is great. Its probably the best skill in the game. Seriously. Its also on the Loremaster skill list, so use those levels to drop as many points into it as possible.
Really, as a sorcerer, with Cha focus instead Int, its hard to get all the skills you need. I'd keep one social skill maxed (Bluff is a class skill for sorcs), along with Concentration. Then put some points in knowledges to qualify for Loremaster and in Spellcraft to qualify for Archmage. Other than that, keep UMD up and you should be good.
Also, don't forget your +5 ability points over 20 levels that you'll be putting in Cha, and probably your +6 Cha cloak at some point, and maybe even a Wish or 2 if you are lucky. Those all factor into your skill checks as well!
Also, Sense Motive is only a class skill for a select few classes. Most monsters and most NPCs won't have very many, if any, ranks in it. Your biggest issue would be pulling a fast one on Rogues, Bards, Clerics, and Paladins, although Clerics and Paladins don't have a ton of skill points to be throwing around anyway so they probably won't be much of an issue unless the NPC is a high level cleric judge or lawyer or something...