Sellers will have to think about this individually. From the messages in the forums, a lot of sellers are already finding sales this year are lower than they hoped or expected.
Nobody can afford to make a loss on postage so I would guess a lot of sellers, private and business, will have to put prices up.
Second Class Large Letters, which I use for the bulk of my low cost little items, has not gone up so I won't change the price for that.
I am also planning to switch from Second Class Signed For LL to 48 hour Tracked - which is unsigned but gets delivery confirmation. At £2.70, it will be a lot cheaper than Signed For - and Signed For compensation has dropped to £20.
So, personally, no price rises for me.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)