Raspi is likely going to continue making moves like this, since they have gone public. You can't just have people buying the cheaper 1GiB boards and upgrading them to 4GiB, that's taking potential profits away from the investors...
I doubt many are doing this upgrade, and I think its awesome someone has the tooling & skill to do so. I cannot fathom how this is a threat to RPI. I would assume a community firmware patch will likely release & resolve the limitation (until it becomes a signed binary)
> until it becomes a signed binary
It's already a signed binary, with rollback protection. (According to Reddit comments; I stopped using Raspis a long time ago)
Consider the alternative where a bigger number of modded boards with dubious RAM gets into circulation, which is no problem for Chinese companies to do. It would quickly result in a distrust of all RPi products and everyone would suffer.
It also has nothing to do with going public, it is consistent with what they were always doing: it never was fully open, in fact quite the opposite and they were always protective about their HW, you can't even order the SoC as a separate chip, only as a part of premade/customized board.