Todd said it himself more or less.

That fireblast in the dungeon in the trailer was two fire spells in both hands. Perhaps it was a special version of the fire spell, as fire surrounded the player.

We don't know if we can combine different spells (ice in one hand, fire in the other) yet, but Todd said they were messing with it and wanted to have it.

None of this actually have anything to do with spell making though...

I guarantee if Skyrim doesnt ship with spell creation, it will be modded in. If a modder can do what Beth cant then thats a problem. This does nothing for console players though, so we need spell creation in. Spell creation is deeper than attaching spells to both hands and feet.

Problem with that though is a modder can focus on just spell creation while Beth has to complete the overall massive project that is Skyrim.

I'm hoping that differing spells of the same basic element (fire in this case) have different effects when combined. So fire spell 1 on each hand produces a super charged fireball, where as fire spell 2 produces what we saw in the trailer. Perhaps with the first spell being a ranged attack, and the second being a touch spell. To me that is a system that has a lot more potential than spell making.

Probably not explained that very well.

I'd prefer it if you just started out with some basic effects and can refine these into different forms later on using perks.

I think there will be different spells of the same element yeah. They can't fit all those combinations in one spell.
If they actually manage to combine different spell elements and such (like everyone talked about on the forums before), then yeah, I also think it has a lot more potential. In a way, it will be like creating "new spells".

I was under the impression todd said this was just one of the ways you could use the fire spell, not a combo.(i could be completely wrong though) I remember in an interview he said you would have your fire spell or w/e andddd you could use it in a specific way i think his examples were
a) shoot a fireball at range
b)area of effect blast radius
c)i remember him saying you could also place a circle of fire or something on the ground and when someone walked over it it acted as a trap and burst into flames.

edit: Ajwol below explained it better hah

The fire spell example we was giving was a basic range attack, holding the trigger down for a contuaal flamethrower like burst, placing a rune on the ground or using the spell in both hands to cast a much bigger fireball. Nothing like what was shown in the trailer has been talked about to the best of my knowledge.