Four Letters

Are four letter gamertags that have three of the same letter within them rare? I'm quite certain that all the combos of four letters in this type of formation are all taken. Do you think they will gain value with time or are they worth anything currently. Please leave your appraisal below

E.g
(SSSE)
(TVVV)

They might gain rarity, just like 3 characters did, so yeah, hold on to them if you have any.