I would be very surprised if Yamato made all of their 1/48 plans based soley on the performance of similar 1/60 items in the market. Where was their 1/60 VF-1S Hikaru? My point is, if fans want a 1/48 set of GBP armor and don't buy the 1/60, Yamato will get wind of it and act accordingly if they care about their meal ticket. Certainly, nothing is 100% guaranteed, but if the profit margin is there, I'd be surprised if they didn't do it.
As tight lipped as Yamato has been about things lately curt, cold responses to fan questions don't surprise me.