Why Glalie as part Fairy? I mean, sure Froslass is part Ghost, but... Glalie... it's probably one of the most menacing, weather-bitten, grim, harsh Pokémon out there. Yes, it does scream "I want a second type" at the top of its icy lungs, but I suspect it has Dark or Rock in mind when saying that (Its Ruby dex entry reveals it's not as much a ball of ice as it is an ice-covered rock, whereas it has ALL the staple Dark moves in its movepool). If GameFreak wants to retcon an Ice Pokémon into part Fairy, I think the Vanillite line would suit better. Or even better, just make a new one. How much of a stretch would a dancing snowman be?
As for new type combinations, Dark/Electric would be interesting to see (or just retcon Luxray already). Ice/Anything would be terrible on the defensive side, but it looks would probably keep it very memorable anyway. Grass/Dragon is long overdue, but if the "starter types in reverse order" pattern with Palkia and Reshiram is anything to go by, perhaps we'll get one this generation (Grasping at straws, you say? Seeing patterns? Forgetting Kingdra? Nonsense.).
Bug is paired with most types except for Normal as well as the four "late-game" types; Ice, Dark, Psychic and Dragon. I think it's time to fill the holes. Apart from Bug/Normal (or vice versa, though secondary Bug types are rare), most of those would look so badass they would patch up the image of Bug Pokémon as puny early-game beginner 'mons:
Bug/Psychic? I can imagine this one being really trippy. Hypnotic spider with long legs? A Cocoon Pokémon which stays a cocoon, and is moderately powerful to boot? Hive mind ants? Holy golden scarab beetle? Many possibilities here.
Bug/Ice would be cool. I believe CAP's Syclant is Bug/Ice, but can't check due to that portion of the site still being down. Come to think of it, isn't there a Bug/Psychic in there too?
Bug/Dark would be nightmare fuel. A proper scorpion. A giant black spider. A hairy, long-legged something that likes to hide (à la Diglett, Shellder or Tangela), only showing off claws or legs peeking out from its cover. Or perhaps they'd just pull a Joltik and make it adorable.
Bug/Dragon.... well, this would certainly be interesting. As long as the designers put any decent amount of thought into it, it could not possibly go wrong. But if rushed... oh my, we'd get a good laugh.
Bug/Normal... Spider-Man?