No, by all means take advantage of the RFS availability as Gold and book now if it's a key route. The Gold extra availability works best on medium term bookings, close up to the travel date the Gold benefit probably will fade away, but very close up availability for everyone tends to be quite good, except for understandable exceptions (e.g. commuter routes on Monday mornings, school holidays in the UK). Having made the booking it won't be blocked by going to Silver.

The one area where you may be hit, at least for the time being, is that you may lose seat assignments. This falls into 2 groups, the ones you should lose by becoming Silver: front rows of CE, front rows of Domestic; secondly the ongoing bug on exit rows, you may lose seat assignments there too. But you should be able to select other seats without trouble.