Go5G Plus -> Next for Fold promo

I have 12 lines so the upgrade would cost $1440 a year. But judging by the fold8 promos I’d get $800 more trade in credit per upgrade. Worth the move? Can we still do the move if we are grandfathered in? Edit: Biggest concern is they drop Go5G Next from the best deals and now I’m stuck with a more expensive plan. Thoughts?