Oh, nice. Can we also expect the getblocks message to be deprecated some day along with this improvement? I don't see any other use than legacy from now on.

One more thing: I currently sync both headers and blocks with a single node and I'd really like to take advantage of the parallel download, but I don't get the 'moving window' approach in detail without diving into the Bitcoin Core code. I'd very naively guess you're requesting one or a few different blocks at a time from each connected peer to fill the 'window' and you only keep moving it (going for higher heights) as the lower side of the window is filled (i.e. older blocks are downloaded). Another fix for multiple download would be assuming the blocks may come in an unordered fashion. Is this optimal for SPV or even correct at all? Perhaps a much wider window due to the trivial size of filtered blocks?