I bought BD a few weeks ago - for 68 cents - even for an old game on sale, it's too cheap - basically no profit. It makes me think that official support for it will soon end? Has Larian announced anything that would support this speculation on my part?
No.
When Divinity 2 was released on GOG, there was a pay what you want promotion where Divine Divinity could be had starting at 1 cent, Divine Divinity and Beyond Divinity are part of a Divinity Anthology with the Developer's Cut release of Divinity 2 and bonuses in the D:OS EE Collector's Edition, etc. There are much younger games that end up being sold cheaper in bundles, etc (in some cases as a promotion, like Divine Divinity being given away a couple times in GOG promotions).