The point of a 5-step plan is that each step builds on the last. "Step 5" becomes easier/cheaper/quicker by having a "step 4". So RX-51 will have the best hardware that Nokia can afford to put in it at the price point it's targetting, and will have the best software that Nokia can develop in the time available.

There won't be a discussion of "well, this is step 4 so let's not make it nice and usable"; there'll be discussions of "well, if we do this nice feature it may sell better, but it'll push the release date out"; or "the hardware's not up to it, but by the time the N1000 comes out with Harmattan, there'll be more grunt to play with".