Bitcoin deflation != Historical deflation.
The difference is that when Bitcoin deflates it is instantaneous and world-wide (instant arbitrage opportunity). Bitcoin deflation encourages spending rather than saving because the global economy demands it, contrary to the past deflation of weighted coins, it created a position where the older coins were more valuable than the newer coins. Those coins were not likely to be spent because they were worth more than the face value of the coin.
When gold backed currencies where a "thing" no one much cared about the face value or even which country (as long as the mint was trusted) minted the damn things, indeed the face value was directly tied to weight, all anyone cared about was the gold weight. I'm not sure where you do the idea that they would deflate older coins by minting new ones with less weight and same face value, that's just daft; the gold would simply be remelted - it did not remove gold from circulation (deflation).. Your probably thinking of bullion coins being minted today with metal of value much higher than face...which is a post fiat construct, that has nothing at all to do with gold back currencies.
Bitcoin deflation would encourage spending in 2030 the same way that it does on these forums in 2014, which can be summed up in "I bought a 150k dollar pizza in 09' and we are the new wealthy elite". Any financial system with a highly deflationary currency like bitcoins would ball up and die, as no funds would ever move through the system; Inflation pushes smart money to invest in creating means of production, in to research, and building income producing properties while all that deflationary currency encourages is the building of Scroodge McDuck banks (which in the case of bitcoins you cant even swim through).