From what I have heard from the technical experts (bbc and autosport) they think that Marrussia may be able to make that step because they have redesigned most of their car and made many improvements, whereas Caterhams car is more of a slight evolution from last years car.
Marussia's car is all new, yeah, but it's such a pig of a car I can't imagine them being better than last year at all, especially considering their driver line up. I imagine Bianchi will be able to put in some results closer to the points, but I kind of doubt they'll even score this year. Their car's proven to have the least downforce, and you can't have that going into a track like Albert Park.
The Caterham's concentrating on refining their package from last year, it's a smart move imo. They've laid out a solid plan, where they'll be using the first few races as almost mainly data gathering (ghetto testing) in order to for their big debut in Spain, which they've said they plan to give their car its first big upgrade at, so look for a big change then.
I think that in Melbourne they're really going to be struggling to find speed with the Supersofts since no one's tested it enough besides Ferrari really. The set up will be even tougher for Marussia though.
It's been very quiet so far about Red Bull, it all seems to be Lotus, Perez and Mercedes... so I fully expect for Vettel to dominate this 2011-style.
If he doesn't well I'll be happy, as long as no-one else does.
RB's been doing nothing but complaining about how they "didn't have enough time to test." which sounds like a pretty weak bluff to me. They keep trying to distract every one by saying things like, " We're watching the competition closely" "Don't underestimate [team/driver]" blah blah. They're smirking and really confident. In tests, guys reported seeing the RB9 and the E21 (Lotus) as being the most stable through the corners, and we all heard about how RB has "10%" (rule of thumb estimation) more downforce than anyone else. By all accounts, they should have the first race in the bag, but you just never know, the tests didn't have ideal conditions to let them know exactly how the tires would work out for them, so we're all gonna find out this weekend.
I'm really looking forward to what Mercedes can do here. They seem to have a really quick package according to miffy testing results, but, again, we'll find out exactly what that translates to in application.
My prediction is that we'll have a fierce Q3 session on Saturday that'll have us jumping out of our seats.
If McLaren sets a fast time in Q, then I have a bad feeling they'll only fall back during the race due to trouble with getting to grips with consistency with this new rubber and their revised suspension work.
I have a weird feeling Lotus is going to sneak their way up through everyone to give a good battle to RB and company.
Anyway, my predictions are: 
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