steam lets you do manual version selection, so if you really want to you can keep playing old versions forever.
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personally i have already made peace with the fact that my current saves will all be bricked when 2.0 hits, and that it will probably take a while for all the mods i like to be updated for 2.0. i'm pretty optimistic that things are going to be fine in the long run, with all good mods eventually being ported to 2.0 or replacement mods showing up to fill the void left by the ones that are abandoned.
i dont think a factorio 2 was ever a thing, never heard wube mention anything like that