Not weirdly, that's the point of the whole announcement. You can't get OpenTTD on its own from Steam anymore, it comes with TTD now https://store.steampowered.com/app/3766810/Transport_Tycoon_...
https://store.steampowered.com/bundle/70574/Transport_Tycoon...
But the OpenTTD item listed in the bundle is non-existent at the moment.
Since the bundle is a separate purchase option and not replacing the option to buy TTD on its own, it also allows people to easily find out what they're in for by providing a description of what OpenTTD is, as opposed to just buying TTD on its own.