I think Messi will not go anywhere. ~~~ Plus Messi will age one year and hardly anyone will need it as a player, although his name will still work for marketing.
Who knows? You must know that age isn't a big problem if the player still can take advantage of the team. Even if Messi will age one year more, I am pretty sure that the interest from other clubs won't disappear. Look at Zlatan Ibrahimović, he was already more than 35 years old but AC Milan still bought him on the previous transfer season (Jan 2, 2020). As long as Messi has no problem with his physical health, then there is always a chance for him to move.
Also Ronaldo did it, Messi will not be as he was in his prime but, Messi would play even after one year addition, Messi had not less than twenty assist last season and his assist record are impeccably awesome, he can be played in a sit back role assisting the forwards. There are players that beats age barriers and Messi would be one.