Don't ask LinuxPhoneApps.org (npub1j6f…76l3) about stuff like that, they're only about apps!
I don't think that such a board is likely to happen - but I could see the board of the 'Liberty Phone' (4 GB RAM (the maximum for the SoC) + 128 GB eMMC) land as an upgrade eventually.
The big issue is: Will it still be a relevant enough upgrade once Purism can afford offering this (from an inventory/financial perspective)? Doing this too early (at a nice price) would obsolete remaining 3/32GB inventory.