But you can keep all your unlocks and have room still for a crap load of others
10 columns of boxes 5 rows thick = 50
3 weapons roughly with 9 classes ~= 27 weapons. At max of 29 due to only 1 being added for spy and engi, the unknowns in this all.
This leaves 2 weapons min with the other classes for extra items. Max 3 with other classes only having 2.
Also, the TF2 stat clearing is only for TF2. Steam still has them. So you can get the fancy almost killed 99 people thing without losing how much time you played ??? class.