That is certainly true if the price is constant. However, news of a burn can drive significant demand, and could easily offset the reduction in supply. If the price multiplies several times - not uncommon in the crypto world, as we all know - the end result could be a market cap that's far higher, despite the lower supply.

It's not clear to me as to which of these methods will be considered favourable by the wider crypto community, but burning does seem popular with the Steem community, judging by the many comments to this post. Personally, I'm leaning towards #6, though I'm aware realistically there'll be a bit of #2 and #3 as well.