Hi AliMusa,
No. Better manufacturers and retailers don’t generally “negotiate” (see post #6 here) or have “fake sales” with large discounts based on the time of year or holidays (see the guidelines here and post #5 here). While they may occasionally have sales with smaller discounts or sell floor models at a reduced price … I would treat retailers or manufacturers that negotiate their prices or have “major holiday sales” at certain times with “huge” discounts as a red flag because manufacturers or retailers that sell good quality/value mattresses don’t need to negotiate or have “fake sales” with misleading discounts to create a false sense of urgency as a sales tactic and they sell good quality/value mattresses every day of the year at good prices that are already very fair and reasonable.
It’s certainly possible that if you lose a significant amount of weight that your needs and preferences in a mattress could change but you can always add a topper if you need some additional softness and pressure relief and there are also component mattresses available with replaceable layers and components that allow you to adjust the comfort and support of a mattress after a purchase by rearranging or replacing layers without having to replace your entire mattress if your needs and preferences change after a purchase.
Phoenix