Can totally assume that PS4 and Xbox One will be more expensive, I got Infinity on the Wii U, and not so sure if there will be many differences that justify jumping over to PS4, If you can place more items in the toy box i may be somewhat tempted. even at the extra £5-10.
Of course assuming that there will also be packs without an infinity base, I wouldn't bank on them being cheaper yet, sure will retail at less, but we don't know if these packs will come with all 3 figures the starter pack does, they may do the whole Skylander's thing where the booster pack for giants only came with one figure, therefore it may work out more cost effective to just opt for buying the starter pack anyway.
Either way we will have to see! it seems strange they didn't announce a version without the infinity base though, so fans like us who are wanting to pre-order don't have to wait around.