If that horror scenario realizes, I cannot see them reusing the existing branding. It just wouldn't make sense to call the expensive Value brackets as Basic and the current Pro brackets as Value.

And realistically, nobody buys M and K if they have the choice. It's just too expensive for just a little bit of flexibility. If there was demand, I would think that there would be a more straightforward away to book them than call CS.

I think it's more likely that they either keep the current system with 3 types in economy, and add 2 types in premium. Or that they go back to the old system with just to 2+2(+2), meaning discount and flexible in all cabins, with optional bundles on top.

Besides, I don't really the problem with keeping Pro at 150%, regardless whether discounted PE earns 100% or 150%. Only the most careless and unpoliced of flyer would squander somebody else's money on Pro just for the mileage. That guy can continue to buy Pro at 150% or switch to Premium, depending what his policy allows.

I can totally see Premium Flexible earning the same 150% as Pro, while Premium Saver would either continue to earn 100% (as it does in codeshares) or be upgraded to 150%.