A few things would be worth pointing out.
Gabor Talmasci (sp) also tried the same move for 2008, wasnt a great plan. The bike was'nt great, but he wasn't able to rack up a year, dispite being the then 125cc world champion.
As Miller is likely to be the world champ of Moto3 this year, you need to look at the standard route.
But people have compared him to Marquez, and as he's basically the revalation of the decade, we need to look at MM and his route.
Did 3 years in 125cc and really struggled, got on the Moto3 BAM. moved to Moto2, took 2 years after being basically win it or bin it, wins the second year (good work nontheless). Goes to MotoGP and wins in his first year by 4 points against the mighty Jorge (but likely wouldve taken another year if it not for suspect moves on his team mate and JL getting hurt). He'll win it this year.
Now the important thing throught this is that MM has spent a lot of time building up to this. Could MM bypass Moto2's 2 years? I would certainly doubt it to get the same result....
But then again, will he win on another other bike than a Marc VDS Kalex if he went to Moto2 next year? OOoooohhhhhhh he said it !!!
I feel in fairness, he's bit the hand that feeds and if he gets stuck on a crap bike in Moto2, he'll be there for too long.
My thoughts anyway.